A new class of low-molecular-weight amphiphilic gelators

Article abstract of DOI:10.1002/chem.200400716

A new powerful class of low-molecular-weight amphiphilic compounds has been synthesized and their structure-property relationships with respect to their gelation ability of organic solvents have been investigated. These compounds are able to gel organic solvents over a broad range of polarity. Especially polar solvents such as valeronitrile and γ-butyrolactone can be gelled even at concentrations far below 1 wt %. It was found that the gelation ability of these asymmetrically substituted p-phenylendiamines depends on a well-balanced relation of the terminal head group, the units involved in hydrogen bonding (amide or urea groups), and on the length of the alkyl chain. With this class of new gelators it is possible to tailor thermal and mechanical properties in different organic solvents and open various application possibilities.

Full text of DOI:10.1002/chem.200400716

FULL PAPER
A New Class of Low-Molecular-Weight Amphiphilic Gelators
Nils Mohmeyer and Hans-Werner Schmidt*[a]
Abstract: A new powerful class of low-
molecular-weight amphiphilic com-
pounds has been synthesized and their
structure–property relationships with
respect to their gelation ability of or-
ganic solvents have been investigated.
These compounds are able to gel or-
ganic solvents over a broad range of
polarity. Especially polar solvents such
as valeronitrile and g-butyrolactone
can be gelled even at concentrations
the terminal head group, the units in-
volved in hydrogen bonding (amide or
urea groups), and on the length of the
alkyl chain. With this class of new gela-
tors it is possible to tailor thermal and
mechanical properties in different or-
ganic solvents and open various appli-
cation possibilities.
far below 1 wt%. It was found that the
gelation ability of these asymmetrically
substituted p-phenylendiamines de-
pends on a well-balanced relation of
Keywords: amphiphiles
·
amphi-
philic gelators · gels · self-assembly ·
supramolecular chemistry
Introduction
stroyed upon heating and reformed during cooling. In the
literature 1,3:2,4-di-O-benzylidene-d-sorbitol (DBS),[17] cho-
lesterol derivatives,[18] bolaform amides,[19] symmetrical di-
alkylamides,[20] symmetrical bisureas,[3,4,21] and N-n-octyl-d-
gluconamide[22,23] are examples of investigated organogela-
tors. An analysis of the utilized building blocks of gelator
molecules indicates that an efficient organogelator must
contain defined molecular units. Important factors are geo-
metrically defined ring systems, functional groups like
amides or urea units to form hydrogen bonds, and long alkyl
chains to tune the melting point and the solubility.[4]
The various combinations of these molecular units moti-
vated us to synthesize a new class of asymmetrical substitut-
ed para-phenylendiamines based on readily available start-
ing materials and simple organic reactions. The different
structural units were varied in order to systematically ex-
plore their influence on the gelation ability, especially with
regard to the sol–gel phase-transition temperature and the
mechanical properties. In the literature the gelation ability
of most gelators is examined, in addition to apolar solvents,
in polar solvents like THF, acetone, or methanol. Of special
interest to us is the gelation of polar solvents such as g-bu-
tyrolactone and valeronitrile with respect to their applica-
tion possibilities as solvents in dye-sensitized solar cells.[24–27]
Organogelators are a family of low-molecular-weight organ-
ic molecules that can gel organic solvents at low concentra-
tions. The subject of organogels has generated enormous in-
terest due to industrial potential in different areas ranging
from cosmetics to advanced materials.[1–16] The process of
self-assembly of these small organic molecules into supra-
molecular structures is complex and different for each indi-
vidual compound. However, although the sequence of the
gelation process is understood, up to now it has been impos-
sible to predict from the molecular structure the gelation ef-
ficiency in a given solvent. Low-molecular-weight organic
gelator molecules are capable of self-organizing into finely
dispersed anisotropic structures within the organic solvent,
forming a three-dimensional network resulting in gelation.
Specific noncovalent interactions of gelator molecules such
as hydrogen bonding, hydrophobic interactions, p–p interac-
tions, electrostatic interactions, and metal-ion coordination
can be employed and are required to form the supramolec-
ular aggregates and subsequently the three-dimensional net-
work structure. These structures are thermoreversible, de-
[a] N. Mohmeyer, Prof. Dr. H.-W. Schmidt
Macromolecular Chemistry I
Bayreuther Institut fꢀr Makromolekꢀlforschung (BIMF) and
Bayreuther Zentrum fꢀr Grenzflꢁchen und Kolloide (BZKG)
University Bayreuth, 95440 Bayreuth (Germany)
Fax : (+49)921-55-3206
Results and Discussion
The gelation ability of the synthesized low-molecular-weight
compounds in organic solvents depends strongly on the
E-mail: hans-werner.schmidt@uni-bayreuth.de
Chem. Eur. J. 2005, 11, 863 – 872
DOI: 10.1002/chem.200400716
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863

structural fragments of the molecules. Therefore we have
varied systematically the different units within the amphi-
philic molecule. The investigated molecules consist of three
different structural units, shown here: an apolar terminal
head group, a hydrogen-bonding segment based on p-phe-
nylendiamines, and a long alkyl chain with more than eight
carbon atoms.
quently treated with three different aliphatic acid chlorides.
These urea/amide-functionalized derivatives 7a–c are iso-
meric structures of compounds 4a–c. Only the position of
the amide and the urea unit are changed. The corresponding
bisureas 8a–c to the bisamides 3a–c were synthesized by the
addition of amino compound 6 to the three different isocya-
nates. With the synthesized amphiphilic molecules we want
to investigate the structure–property relationships with re-
spect to their gelation ability in organic solvents. Especially
the well-balanced interactions of the terminal head group,
the hydrogen-bonding unit, and the alkyl chain are the
major factors to tailor efficient organogelators.
Structure–property relationships on the gelation ability: In
the following we would like to discuss the influence of the
different structural units on the gelation behavior. The aim
is to find a well-balanced situation of attractive and repul-
sive forces and to optimize the gelation efficiency. First, the
influence of the terminal head group of the asymmetrically
substituted p-phenylendiamines on the capability to gel or-
ganic solvents is discussed. We compared the gelation ability
in p-xylene of two series of compounds at a concentration of
1 wt%. For this purpose, mixtures of each compound in p-
xylene were heated until the solid was completely dissolved.
The resulting solution was slowly allowed to cool to room
temperature and gelation was visually observed. Gelation
was considered to have occurred when a homogenous
sample was obtained that exhibited no gravitational flow.
This process was repeated many times, demonstrating the
thermoreversibility of the gelation and dissolution process.
The molecules of the first series were the asymmetrically
substituted p-phenylendiamine-based bisamide derivatives
3c–e. They all have an alkyl chain with seventeen carbon
atoms and the same hydrogen bonding unit, but have differ-
ent terminal head groups. Compound 3c has a flexible cyclo-
hexane ring, 3d an aromatic phenyl ring, and 3e a bulky
tert-butyl group. The derivatives 4c–e were used as a com-
parison; they have the same terminal groups but one of the
amide groups has been replaced by a urea group with a -C14
moiety. Table 1 shows the initial trend of the gelation ability
of these kinds of molecules in p-xylene. Within both the bi-
samide derivatives 3c–e and the amide/urea-functionalized
In this work we selected as terminal head group an aro-
matic phenyl, a cycloaliphatic cyclohexyl, and a bulky tert-
butyl group. Within the hydrogen-bonding segment amide
and urea units were selected.
Synthesis of the amphiphilic molecules: The synthetic routes
to the asymmetrically substituted p-phenylendiamine-based
bisamide derivatives 3a–e and amide/urea functionalized de-
rivatives 4a–e are shown in Scheme 1. In the first step 4-ni-
troaniline was treated in dry N-methyl-2-pyrrolidone (NMP)
and triethylamine with the different acid chlorides, benzoyl
chloride, cyclohexane carboxylic acid chloride, and pivaloyl
chloride. These acid chlorides were selected to represent ar-
omatic, flexible cycloaliphatic, and bulky aliphatic end
groups. The resulting nitro compounds 1a–c were reduced
with hydrogen, using palladium on activated carbon as cata-
lyst, to the corresponding amine derivatives 2a–c. These dif-
ferent amines were treated with aliphatic acid chlorides of
different chain lengths resulting in a series of asymmetrically
substituted p-phenylendiamine-based bisamide derivatives
3a–e. For cyclohexane-based derivatives 3a–c we chose oc-
tanoyl chloride (3a), tetradecanoyl chloride (3b), and octa-
decanoyl chloride (3c) in order to discuss the influence of
the chain length on the gelation ability. To discuss the influ-
ence of the terminal head group we treated the phenyl- (2b)
and tert-butyl-terminated amines (2c) to the octadecanoyl
chloride to obtain bisamides 3d and 3e. The amide/urea-
functionalized compounds 4a–e were synthesized by the ad-
dition of amino compounds 2a–c to the different isocyanates
(-C8, -C14, and -C18 chain length). This resulted in the amide/
urea-functionalized derivates 4a–e, which can be compared
with the bisamides 3a–e to discuss the influence of the type
of hydrogen-bonding unit on the gelation ability.
Table 1. Comparison of different terminal groups with respect to the ability
to gelate p-xylene at a concentration of 1 wt%.
The synthetic route to obtain the urea/amide-functional-
ized derivatives 7a–c and the bisureas 8a–c (Scheme 2)
starts with the reaction of cyclohexylamine with nitrophen-
yleneisocyanate. The resulting nitro compound 5 was re-
duced to amino compound 6 in a procedure similar to that
used in the synthesis of compounds 2a–c by using palladium
on activated carbon. To retrieve the urea/amide-functional-
ized derivatives 7a–c, the amino compound 6 was subse-
3c
gel
3d
no gel
3e
no gel
4c
gel
4d
no gel
4e
no gel
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Amphiphilic Gelators
FULL PAPER
ability depends strongly on the
balanced intermolecular inter-
actions of the hydrogen-bond-
forming units. In these cases,
the bulky tert-butyl group could
disturb the intermolecular inter-
actions of the adjacent amide
group so much that the gel
state cannot be reached. Also,
the derivatives with a terminal
phenyl group as a conjugated
planar rigid unit are not able to
form gels. As a result it seems
that the flexible cyclohexane
ring as a terminal head group in
this class of molecules promotes
the intermolecular interactions
of the hydrogen-bonding unit
for p-xylene in the required
way.
The second comparison dis-
cusses the structure–property
relationship of the gelation abil-
ity with respect to the influence
of different hydrogen-bonding
units in combination with the
length of the pendent alkyl
chain. We investigated the ge-
lation ability of selected mole-
cules in p-xylene as an apolar
hydrocarbon, and in valeroni-
trile and g-butyrolactone as
more polar solvents. The last
two solvents are of immense in-
terest with regard to their po-
tential application in dye-sensi-
tized solar cells.
Table 2 summarizes the mini-
mum required additive concen-
tration necessary to form
a
stable gel. If a gel is not formed
the molecules are either insolu-
ble (insol) at the boiling point
of the solvent or they precipi-
tate (ppt) during the cooling
process. The structure of the
hydrogen-bonding unit was sys-
tematically varied. Starting
from the bisamides 3a–c, the
Scheme 1. Synthesis of asymmetrically substituted p-phenylendiamine-based bisamide derivatives 3a–e and
amide/urea-functionalized derivatives 4a–e.
derivatives 4c–e, the cyclohexyl-terminated derivatives 3c
and 4c are the only ones to gel p-xylene at a concentration
of 1 wt%. In both cases transparent stable gels were ob-
tained. The derivatives with phenyl (3d, 4d) or tert-butyl
(3e, 4e) groups exhibit no gelation ability. The molecules
precipitated during cooling from solution. These results
show that in p-xylene the terminal head group of this class
of molecules greatly affects the gelation ability. The gelation
amide groups were successively replaced by one urea group
yielding amide/urea- and urea/amide-functionalized deriva-
tives 4a–c and 7a–c, respectively, and subsequently the bis-
urea series 8a–c. In addition, the length of the aliphatic
chain was increased within each of these four classes from 7
(a), to 13 (b) and to 17 carbon atoms (c). Although the
chemical structures of the presented molecules are rather
similar, only selected compounds are efficient gelators. Most
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H.-W. Schmidt and N. Mohmeyer
by the additional asymmetry.
By changing the position of the
amide and urea groups in the
molecule (7a–c) the gelation ef-
ficiency decreases. The mini-
mum required additive concen-
tration in p-xylene is in the
range of 0.6–0.8 wt%. Com-
pound 7a, with the shortest
(octyl) alkyl chain is not soluble
in boiling p-xylene. The re-
placement of the second amide
group by a urea leads to the ob-
tained bisureas 8a–c, which are
completely insoluble in boiling
p-xylene. These results indicate
that the intermolecular interac-
tions increase proportional to
the number of introduced urea
groups, at the expense of solu-
bility in boiling p-xylene.
This trend was also observed
in the two investigated polar
solvents, valeronitrile and g-bu-
tyrolactone. The amide/urea-
functionalized class of com-
pounds 4a–c are by far the best
gelators and are able to gel
these polar solvents. For valero-
nitrile the most efficient orga-
nogelator is compound 4c. Gels
were obtained at a concentra-
tion as low as 0.05 wt%. By de-
creasing the length of the alkyl
chain the gelation efficiency in
valeronitrile decreases. The re-
Scheme 2. Synthesis of asymmetrically substituted p-phenylendiamine-based urea/amide-functionalized deriva-
tives 7a–c and bisurea derivatives 8a–c.
Table 2. Minimum required concentration given in wt% of the compounds 3a–c, 4a–c, 7a–c, and 8a–c to
form a stable gel in different solvents (insol: compound is not completely soluble at the boiling temperature of
the solvent; ppt: additive precipitates during the cooling process).
n
p-xylene
valeronitrile
g-butyrolactone
3a
3b
3c
6
12
16
1.1
1.5
1.5
ppt
ppt
ppt
ppt
ppt
0.5
4a
4b
4c
7
13
17
0.3
0.25
0.2
0.5
0.25
0.05
ppt
1.0
0.75
quired
concentration
is
0.25 wt% for 4b and 0.5 wt%
for 4a. The bisamide deriva-
tives 3a–c precipitate in valero-
nitrile upon cooling, whereas
the amide/ureas 7a–c and bis-
ureas 8a–c are, with the excep-
tion of 8c, not completely solu-
ble in valeronitrile even at boil-
ing point. Surprisingly, com-
pound 8c with the longest alkyl
chain is able to form a gel at a
concentration of 0.2 wt%. The
7a
7b
7c
6
12
16
insol
0.8
0.6
insol
insol
insol
insol
insol
insol
8a
8b
8c
7
13
17
insol
insol
insol
insol
insol
0.2
insol
insol
insol
of the investigated compounds show good gelation efficiency
in the nonpolar solvent p-xylene. The minimum required
concentration of the bisamides 3a–c in p-xylene is about 1–
1.5 wt%. However, the amide/urea-functionalized deriva-
tives 4a–c are able to gel p-xylene at much lower concentra-
tions, that is, 0.2–0.3 wt%. This more efficient gelation is
caused by increasing the intermolecular interactions through
the replacement of the amide moiety with a urea group and
results in g-butyrolactone are similar to those in valeroni-
trile. From the amide/urea series, compounds 4b and 4c
form stable gels at 1.0 and 0.75 wt% respectively, whereas
compound 4a precipitates during cooling. The urea/amides
7a–c and the bisureas 8a–c are not soluble enough in g-bu-
tyrolactone. Surprisingly, an efficient gelator was found in
compound 3c, the bisamide with the longest alkyl chain. Ge-
lation occurs readily at 0.5 wt%. The derivatives 3a and 3b
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Amphiphilic Gelators
FULL PAPER
precipitate during cooling and do not form a gel. The optical
appearance of the gels is also different. All p-xylene gels are
transparent, whereas the gels of g-butyrolactone are opaque.
The transparency of valeronitrile gels increases with de-
creasing gelator concentration with all investigated com-
pounds. The differences in the optical appearance of the
gels can result either from differences in refractive indices
or from differences in the width of the fibres forming the
gel.
The morphology of the different organogelators was in-
vestigated by transmission electron microscopy after evapo-
ration of the solvent. Figure 1 shows the transmission elec-
tron microscopy pictures of the dried three-dimensional net-
work of amide/urea-functionalized derivatives 4c, 4c, and
the bisurea 8c gelled at 0.5 wt% in valeronitrile. The elec-
tron micrographs show differences in the morphology of the
different compounds. Compound 4b forms fine cylindrical
fibrils in valeronitrile with a diameter of 100–150 nm; com-
pound 4c also forms these fine cylindrical fibrils, but with
lower diameters of 50–70 nm. However, bisurea 8c forms a
more twisted ribbonlike structure with an average width of
100–300 nm. These different morphological structures and
dimensions show the strong influence of the hydrogen bond-
ing and packing in the formation of the supramolecular
structures.
Concentration dependence of gel formation: For selected
compounds the concentration dependence of gel formation
and sol–gel transition was studied in more detail. The ther-
mal behavior of 3c, 4b, 4c, and 8c gels with, in order, g-bu-
tyrolactone, valeronitrile, and p-xylene were investigated by
the dropping ball method to determine the sol–gel transition
temperature (Tgel) of the gels dependent on the additive
concentration. As shown in Figure 2 the Tgel value is de-
pendant on the concentration of the gelator. As expected, in
all investigated gels the sol–gel transition temperatures in-
crease with increasing gelator concentration. Figure 2 dis-
plays comparisons of the sol–gel transition temperatures at
different gelator concentrations of the gels of 4b and 4c in
p-xylene, valeronitrile, and g-butyrolactone. In all cases the
maximum investigated additive concentration was about
3 wt%. The transition temperature Tgel depends on the alkyl
chain length of the gelator. Increasing the alkyl chain length
from derivative 4b to 4c increases the Tgelin all three cases.
At a first look this is unexpected, since generally the melting
point of amphiphilic molecules and liquid crystals is lowered
with increasing chain length.[28,29] However, it seems that in
the supramolecular aggregates of the present amphiphilic
molecules the packing and the formation of the intermolec-
ular hydrogen bonds is stabilized with increasing chain
length. The transition temperatures decrease with increasing
polarity of the solvent. For example at a concentration of
1 wt% of 4c in p-xylene a Tgel value of 1078C was obtained.
With increasing polarity of the solvent, the transition tem-
perature in valeronitrile decreases to 1008C and in g-butyro-
lactone to 848C. Also, the maximum concentration needed
to dissolve these two derivatives is much lower in p-xylene
Figure 1. TEM pictures of network structures a) 4b, b) 4c, and c) 8c after
evaporation of valeronitrile (initial concentrations: 0,5 wt%). Scale bars
are 1 mm.
than in both polar solvents. In summary it was found that
the amide/urea derivatives in particular are efficient gelators
for organic solvents and that the transition temperature can
be tuned by changing the concentration and the chain
length of the alkyl substituent.
In the following we would like to compare the structural
variations of the hydrogen-bonding unit from selected exam-
ples. For this comparison the bisamide 3c, the amide/urea-
functionalized derivative 4c, and the corresponding bisurea
8c were selected. The dependence of the concentration on
the sol–gel transition temperature of bisamide 3c and of de-
rivative 4c in p-xylene is shown in Figure 3 (top). In both
cases the Tgel values increase with increasing gelator concen-
tration. However, the concentration range in which stable
gels are reached differs immensely. With bisamide 3c, a con-
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H.-W. Schmidt and N. Mohmeyer
Figure 3. Sol–gel transition temperature as a function of the gelator con-
centration of bisamide 3c (triangles) and the amide/urea-derivative 4c
(squares) in p-xylene (top) and of the amide/urea-derivative 4c (squares)
and the bisurea derivative 8c (circles) in valeronitrile (bottom) deter-
mined by the dropping ball method.
about 1328C and increases to almost 1508C at 0.75 wt%.
Higher concentrations are not possible due to the limited
solubility of gelator 8c up to 0.75 wt%.
Rheology measurements were carried out on the selected
examples of the best gels. Figure 4 shows a rheology meas-
urement of amide/urea compound 4b in g-butyrolactone
(c=2 wt%) at different frequencies. The viscoelastic behav-
ior of the gels is characterized by the storage (G’) and loss
Figure 2. Sol–gel transition temperature as a function of the gelator con-
centration of compounds 4b (open squares) and 4c (filled squares) in p-
xylene (top), valeronitrile (middle) and in g-butyrolactone (bottom) de-
termined by the dropping ball method.
centration range of 1.75–2.5 wt% is required to obtain a
stable gel with p-xylene. In comparison, the amide/urea-
functionalized derivative 4c gels p-xylene at a lower concen-
tration range from 0.2 to 1 wt%. It seems that this behavior
and also the higher Tgel values achieved for derivative 4c are
due to the increased intermolecular interaction of the hydro-
gen-bonding unit. Additionally, we examined the sol–gel
transition temperatures of 4c and the bisurea 8c in valeroni-
trile. The effect is even more pronounced. The 4c/valeroni-
trile forms, over a broad concentration range, a gel with Tgel
starting at 658C and levelling off between 105 and 1108C.
However, the Tgel values of 8c in valeronitrile are 408C
higher than that of 4c. At the gelator concentration of
0.5 wt% the transition temperature of 8c/valeronitrile is
Figure 4. Dynamic rheological behavior of 4b in g-butyrolactone at a
concentration of 2 wt%. The plot shows the storage modulus G’ (filled
triangle) and loss modulus G’’ (open triangle) versus frequency.
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Amphiphilic Gelators
FULL PAPER
(G’’) moduli, which are independent of frequency over the
range from 0.01–10 Hz. At this concentration the storage
modulus G’ is about 10 kPa. The value indicates a good re-
sistance against mechanical stress.
Derivative 4c forms stable and transparent gels in valero-
nitrile between concentrations of 0.5 to 2 wt%. Figure 5
shows the different storage moduli of 4c/valeronitrile gels at
Figure 5. Comparison of the elastic storage modulus G’ values versus fre-
quency at different concentrations of gelator 4c in valeronitrile.
Figure 6. Influence of the concentration of the amide/urea-functionalized
derivatives 4b (circles) and the 4c (squares) and bisamide 3c (triangle)
in valeronitrile (top) and in g-butyrolactone (bottom) on storage modulus
G’ (filled symbols) and on loss modulus G’’ (open symbols) at a frequen-
cy of 1 Hz.
the different investigated concentrations. The moduli are
also independent of the frequency. It was found that by in-
creasing the gelator concentration from 0.5 to 2.0 wt%, the
storage moduli increase from 150 to 1200 Pa. However, the
storage modulus of the 4c/valeronitrile gel at a concentra-
tion of 2 wt% is about 2.5 kPa and four times lower that of
the 4b/valeronitrile gel (10 kPa).
Conclusion
Figure 6 compares the influence of gelator concentration
on storage and loss moduli of the two amide/urea-function-
alized compounds 4b and 4c in valeronitrile. In both cases
the storage modulus G’ and the loss modulus G’’ increase, as
expected, with increasing gelator concentration from 0.5 to
2 wt%. The stability of the gel network and the elastic be-
havior both increase with increasing gelator concentration
and thus form a denser network structure. The mechanical
properties of the resulting gels from 4b are substantially
higher than those of 4c. As shown in the transmission elec-
tron microscopy pictures from valeronitrile (Figure 1) the
network structure of compound 4b consists of thicker fibres
that are well interconnected. In contrast, 4c has a finer net-
work structure. This difference may contribute to the higher
values of G’ and G’’ for gels with compound 4b. The same
trend was observed in g-butyrolactone. The storage moduli
of 4b/g-butyrolactone gels are higher than those of 4c in g-
butyrolactone at the same concentration. Compared to the
bisamide 3c gels, both storage moduli of the gels of 4b and
4c are much higher.
In the present work the influence of the chemical structure
on the gelation ability of a new class of amphiphilic com-
pounds is described. It was demonstrated that a well-bal-
anced relationship between the terminal head group, the
groups involved in hydrogen bonding (amide or urea
groups, or combination of both), and the length of the alkyl
chain is required to optimize the gelation ability in organic
solvents. It was possible to find candidates that were able to
gel even polar solvents such as valeronitrile and g-butyrolac-
tone at concentrations far below 1 wt%. Depending on the
employed gelator and the concentration, the thermal and
mechanical properties can be adjusted.
Experimental Section
Materials and methods: Solvents for synthesis were purified and dried
when necessary according to standard procedures. The used amines and
isocyanates were obtained from Aldrich and Fluka and purified by distil-
lation or recrystallization. Solvents for gelation tests were obtained from
Merck-Suchardt and Fluka and used as received. 1H and 13C NMR spec-
tra were recorded at room temperature on a Bruker AC 250 instrument.
IR spectra were recorded on a BIO-RAD Digilab FTS-40 (FT-IR) as
thin films on an Si-Wafer (after evaporation of the solvent on hotstage)
or as KBr pellets. Mass spectra were recorded on a VARIAN MAT CH-
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H.-W. Schmidt and N. Mohmeyer
7-instrument (direct probe inlet, electron impact ionization) at the central
analytic laboratories of the University of Bayreuth. Elemental analysis
was carried out with a EA 3000 (HEKAtech) at the department of chem-
ical engineering laboratory (Prof. A. Jess) of the University of Bayreuth.
25H), 1.71 (m, 3H), 1.87 (m, 2H), 2.00 (m, 2H), 2.36 (m, 1H), 2.51 (t,
2H), 7.40 ppm (s, 4H); MS: m/z (%): 428 (100) [M+]; elemental analysis
calcd (%) for C27H44N2O2 (428.34): C 75.65, H 10.35, N 6.54; found: C
75.45, H 10.37, N 6.49.
N-(4-Octadecoylaminophenyl)cyclohexanecarboxamide (3c): This com-
pound was prepared as described for 1a, starting from compound 2a
(1.09 g, 5.0 mmol) and octadecoyl chloride (1.51 g, 5 mmol). The product
was purified by recrystallization from methanol. Yield 2.1 g of a white
powder (87%, 4.3 mmol); m.p. 2118C; Rf =0.9 (1:1 hexane/THF);
1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d=0.85 (t, J=6.9 Hz, 3H),
1.25 (m, 33H), 1.73 (m, 3H), 1.87 (m, 2H), 2.00 (m, 2H), 2.37 (m, 1H),
2.50 (t, 2H), 7.40 (s, 4H); MS: m/z (%): 484 (100) [M+]; elemental anal-
ysis calcd (%) for C31H52N2O2 (484.4): C 76.81, H 10.81, N 5.78; found: C
76.82, H 10.89, N 5.74.
N-(4-Nitrophenyl)cyclohexanecarboxamide (1a): 4-Nitroaniline (22.61 g,
163.7 mmol) was dissolved in N-methyl-2-pyrrolidone (180 mL) and
added to triethylamine (30 mL) and a spatula-point of LiCl. Cyclohexane
carboxylic acid chloride (18 mL, 136.4 mmol) was added and the mixture
was stirred for 2 h at 808C. After cooling to room temperature, the mix-
ture was precipitated in ice water (500 mL). The mixture was filtered
(glassfilter G3), and the residue was washed with water and dried. Chro-
matography (3:1 hexane/EtOAc) provided the nitro-compound 1 as an
orange–yellow solid (28.6 g, 84%). Rf =0.55 (3:1 hexane/EtOAc);
1H NMR ([D6]DMSO, 250 MHz): d=1.51 (m, 10H)„ 2.35 (m, 1H), 7.83
(d, J=9.2 Hz, 2H), 8.17 (d, J=9.2 Hz, 2H), 10.43 ppm (s, 1H); 13C NMR
([D6]DMSO, 62.5 MHz): d=175.5, 146, 142.1, 125.3, 125, 119, 118.8, 45.3,
29.3, 26.7, 25.4 ppm.
N-(4-Octadecoylaminophenyl)benzamide (3d): This compound was pre-
pared as described for 1a, starting from compound 2b (1.0 g, 4.7 mmol)
and octadecoyl chloride (1.42 g, 4.7 mmol). The product was purified by
recrystallization from THF. Yield 1.46 g of
a white powder (65%,
N-(4-Nitrophenyl)benzamide (1b): This compound was prepared as de-
scribed for 1a, starting from 4-nitroaniline (6.0 g, 43.4 mmol) and benzoyl
chloride (5.04 mL, 43.4 mmol). The product was purified by recrystalliza-
tion from acetone/water. Yield: (8.17 g, 78%). Rf =0.27 (3:1 hexane/
THF); 1H NMR ([D6]DMSO, 250 MHz): d=7.59 (m, 3H), 8.00 (d, J=
6.8 Hz, 2H), 8.06 (d, J=9.3 Hz, 2H), 8.27 (d, J=9.3 Hz, 2H), 10.80 ppm
(s, 1H).
1
3.1 mmol); m.p. 2168C; Rf =0.7 (1:1 hexane/THF); H NMR (5:1, CDCl3,
CF3COOD, 250 MHz): d=0.87 (t, J=7.0 Hz, 3H), 1.27 (m, 28H), 1.77
(m, 2H), 2.56 (t, J=7.4 Hz, 2H), 7.54 (m, 7H), 7.81 ppm (d, J=7.5 Hz,
2H); MS: m/z (%): 478 (38) [M+]; elemental analysis calcd (%) for
C31H46N2O2 (478.72): C 77.78, H 9.69, N 5.85; found: C 77.21, H 9.86, N
5.85.
2,2-Dimethyl-N-(4-octadecylaminophenyl)propionamide (3e): This com-
pound was prepared as described for 1a, starting from compound 2c
(1.1 g, 7.8 mmol) and octadecoyl chloride (2.84 g, 9.4 mmol). The product
was purified by recrystallization from methanol. Yield 2.8 g of a white
powder (83%, 6.1 mmol); m.p. 1968C; Rf =0.8 (1:1 hexane/THF);
1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d=0.86 (t, J=7.0 Hz, 3H),
1.23 (m, 22H), 1.35 (s, 9H), 1.52 (m, 2H), 3.29 (t, J=7.8 Hz, 2H), 7.29
(d, J=7.4 Hz, 2H), 7.46 ppm (d, J=7.4 Hz, 2H); MS: m/z (%): 458 (49)
[M+]; elemental analysis calcd (%) for C29H50N2O2 (458.73): C 75.93, H
10.99, N 6.11; found: C 76.22, H 11.13, N 6.05.
2,2-Dimethyl-N-(4-nitrophenyl)propionamide (1c): This compound was
prepared as described for 1a, starting from 4-nitroaniline (27.63 g,
0.2 mol) and 2,2-dimethylpropionyl chloride (29.53 mL, 0.24 mol). The
product was purified by recrystallization from methanol. Yield: (37.3 g,
85%); 1H NMR ([D6]DMSO, 250 MHz): d=1.24 (s, 9H), 7.94 (d, J=
9.3 Hz, 2H), 8.20 (d, J=9.3 Hz, 2H), 9.77 ppm (s, 1H).
N-(4-Aminophenyl)cyclohexanecarboxamide (2a): Compound 1a (25 g,
100.7 mmol) was dissolved in a mixture of THF (200 mL) and methanol
(40 mL) and Pd/C (0.6 g; 10 wt% Pd on activated carbon) was added.
This mixture was stirred in an autoclave for 24 h at 408C with H2 pres-
sure of 3.5 bar. The colorless mixture was filtered (Alox N) and the sol-
vents were evaporated. The solid was subjected to chromatography on
silica gel (1:1 hexane/EtOAc) to give the slightly magenta amino com-
pound 2a (21.32 g, (97%). Rf =0.25 (1:1 hexane/EtOAc); 1H NMR
([D6]DMSO, 250 MHz): d=1.51 (m, 10H), 2.24 (m, 1H), 4.75 (s, 2H),
5.83 (s, 1H) 6.67 (d, J=8.7 Hz, 2H), 7.05 ppm (d, J=8.7 Hz, 2H).
N-[4-(3-Octylureido)phenyl]cyclohexanecarboxamide (4a): A solution of
compound 2a (1.2 g, 5.5 mmol) in THF (40 mL) was added to a solution
of octylisocyanate (1.06 mL, 6.0 mmol) in THF (40 mL). The reaction
mixture was heated under reflux for 2 h. After cooling to room tempera-
ture, the mixture was added to methanol (80 mL) and evaporated to half
its original volume. The precipitation began while cooling to room tem-
perature. After 2 h the mixture was filtered (glassfilter G3), and the resi-
due was washed with water and dried. The product was purified by re-
N-(4-Aminophenyl)benzamide (2b): This compound was prepared as de-
scribed for 2a starting from compound 1b (7.94 g, 32.8 mmol). The prod-
uct was purified by recrystallization from methanol/water. Yield: (6.9 g,
99%); Rf =0.2 (1:1 hexane/THF); 1H NMR ([D6]DMSO, 250 MHz): d=
4.91 (s, NH2, 2H), 6.54 (d, J=8.9 Hz, 2H), 7.38 (d, J=8.7 Hz, 2H), 7.52
(m, 3H), 7.90 (d, J=7.3 Hz, 2H), 9.86 ppm (s, 1H).
crystallization from THF. Yield 1.83 g of
a white powder (86%,
4.7 mmol); m.p. >2328C (decomp); Rf =0.7 (1:1 hexane/THF); 1H NMR
(5:1, CDCl3, CF3COOD, 250 MHz): d=0.82 (t, J=6.8 Hz, 3H), 1.31 (m,
17H), 1.71 (m, 1H), 1.87 (m, 2H), 1.98 (m, 2H), 2.38 (m, 1H), 3.28 (t,
J=7.4 Hz, 2H), 7.21 (d, J=8.9 Hz, 2H), 7.45 ppm (d, J=8.9 Hz, 2H);
MS: m/z (%): 373 (40) [M+]; elemental analysis calcd (%) for
C22H35N3O2 (372.27): C 70.74, H 9.44, N 11.25; found: C 70.79, H 9.50, N
11.12.
2,2-Dimethyl-N-(4-aminophenyl)propionamide (2c): This compound was
prepared as described for 2a starting from compound 1c (30.0 g,
0.147 mol). Yield: (24.25 g, 94%); 1H NMR ([D6]DMSO, 250 MHz): d=
1.24 (s, 9H), 4.69 (s, 2H), 6.82 (d, J=8.7 Hz, 2H), 7.22 (d, J=8.7 Hz,
2H), 9.62 ppm (s, 1H).
N-[4-(3-Tetradecylureido)phenyl]cyclohexanecarboxamide (4b): This
compound was prepared as described for 4a, starting from compound 2a
(0.74 g, 3.4 mmol) and tetradecylisocyanate (1 mL, 3.6 mmol). The prod-
uct was purified by recrystallization from THF. Yield 1.22 g of a white
powder (79%, 2.7 mmol); m.p. >2308C (decomp); Rf =0.75 (1:1 hexane/
THF); 1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d=0.86 (t, J=
6.8 Hz, 3H), 1.33 (m, 20H), 1.75 (m, 1H), 1.89 (m, 2H), 2.03 (m, 2H),
2.41 (m, 1H), 3.30 (t, J=7.6 Hz, 2H), 7.23 (d, J=8.7 Hz, 2H), 7.48 ppm
(d, J=8.7 Hz, 2H); MS: m/z (%): 457 (25) [M+]; elemental analysis
calcd (%) for C28H47N3O2 (457.37): C 73.48, H 10.39, N 9.18; found: C
73.89, H 10.35, N 9.19.
N-(4-Octoylaminophenyl)cyclohexanecarboxamide (3a): This compound
was prepared as described for 1a, starting from compound 2a (1.09 g,
5.0 mmol) and octanoyl chloride (1.07 mL, 6.6 mmol). The product was
purified by recrystallization from EtOAc. Yield 1.3 g of a white powder
(76%, 3.7 mmol); m.p. 2258C; Rf =0.8 (1:1 hexane/THF); 1H NMR (5:1,
CDCl3, CF3COOD, 250 MHz): d=0.85 (t, J=6.9 Hz, 3H), 1.31 (m, 14H),
1.73 (m, 3H), 1.87 (m, 2H), 2.00 (m 2H), 2.36 (m, 1H), 2.53 (t, J=
8.1 Hz, 2H), 7.40 pm (s, 4H); MS: m/z (%): 344 (95) [M+]; elemental
analysis calcd (%) for C21H32N2O2 (344.25): C 73.22, H 9.36, N 8.13;
found: C 73.23, H 9.41, N 8.12.
N-[4-(3-Octadecylureido)phenyl]cyclohexanecarboxamide (4c): This
compound was prepared as described for 4a, starting from compound 2a
(0.66 g, 3 mmol) and octadecylisocyanate (0.97 g, 3.3 mmol). The product
was purified by recrystallization from THF. Yield 1.26 g of a white
powder (82%, 2.5 mmol); m.p. >2158C (decomp); Rf =0.8 (1:1 hexane/
THF); 1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d=0.86 (t, J=
6.8 Hz, 3H), 1.33 (m, 37H), 1.77 (m, 1H), 1.89 (m, 2H), 2.01 (m,
N-(4-Tetradecoylaminophenyl)cyclohexanecarboxamide (3b): This com-
pound was prepared as described for 1a, starting from compound 2a
(1.09 g, 5.0 mmol) and tetradecoyl chloride (1.7 mL, 6.25 mmol). The
product was purified by recrystallization from EtOAc. Yield 0.85 g of a
white powder (40%, 2.0 mmol); m.p. 2158C; Rf =0.85 (1:1 hexane/THF);
1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d=0.85 (t, 3H), 1.31 (m,
870
ꢂ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 863 – 872

Amphiphilic Gelators
FULL PAPER
2H),2.41 (m, 1H), 3.30 (t, J=7.6 Hz, 2H), 7.23 (d, J=8.7 Hz, 2H),
7.48 ppm (d, J=8.7 Hz, 2H); MS: m/z (%): 513 (28) [M+]; elemental
analysis calcd (%) for C32H55N3O2 (513.43): C 74.80, H 10.79, N 8.18;
found: C 72.46, H 10.53, N 7.85.
(m, 1H), 7.24 (d J=8.7 Hz, H), 7.50 ppm (d, J=8.7 Hz, 2H); elemental
analysis calcd (%) for C31H53N3O2 (499.41): C 74.50, H 10.69, N 8.41;
found: C 73.95, H 10.62, N 8.16.
1-[4-(Cyclohexylureido)phenyl]-3-octylurea (8a): This compound was
prepared as described for 4a, starting from compound 6 (0.8 g, 3.4 mmol)
and octylisocyanate (0.67 mL, 3.8 mmol). The product was purified by re-
N-[4-(Tetradecylureido)phenyl]benzamide (4d): This compound was pre-
pared as described for 4a, starting from compound 2b (1.0 g, 4.7 mmol)
and tetradecylisocyanate (1.29 mL, 4.7 mmol). The product was purified
by recrystallization from THF. Yield 1.2 g of a white powder (58%,
2.5 mmol); m.p. 1838C; Rf =0.55 (1:1 hexane/THF); 1H NMR (5:1,
CDCl3, CF3COOD, 250 MHz): d=0.86 (t, J=6.9 Hz, 3H), 1.31 (m, 22H),
1.77 (m, 1H), 1.58 (m, 2H), 3.35 (t, J=7.4 Hz, 2H), 7.34 (d, J=8.9 Hz,
2H), 7.63 (m, 5H), 7.84 ppm (d, J=8.9 Hz, 2H); MS: m/z (%): 452 (30)
[M++H]; elemental analysis calcd (%) for C28H41N3O2 (451.66): C 74.46,
H 9.15, N 9.30; found: C 74.07, H 9.33, N 9.35.
crystallization from DMF. Yield 0.9 g of
a white powder (64%,
2.2 mmol); m.p. >2098C (decomp); Rf =0.5 (1:1 hexane/THF); 1H NMR
(5:1, CDCl3, CF3COOD, 250 MHz): d=0.87 (t, J=6.9 Hz, 3H), 1.27 (m,
15H), 1.56 (m, 3H), 1.75 (m, 2H), 1.94 (m, 2H), 3.30 (t, J=7.3 Hz, 2H),
3.64 (m, 1H), 7.31 ppm (s, 4H); MS: m/z (%): 388 (14) [M+]; elemental
analysis calcd (%) for C22H36N4O2 (388.23): C 68.01, H 9.34, N 14.42;
found C 68.04, H 9.38, N 14.23.
1-[4-(Cyclohexylureido)phenyl]-3-tetradecylurea (8b): This compound
was prepared as described for 4a, starting from compound 6 (0.3 g,
1.3 mmol) and tetradecylisocyanate (0.4 mL, 1.5 mmol). The product was
purified by recrystallization from DMF. Yield 0.5 g of a white powder
(78%, 1.0 mmol); m.p. >2198C (decomp); Rf =0.6 (1:1 hexane/THF);
1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d 0.85 (t, J=6.8 Hz, 3H),
1.24 (m, 27H), 1.57 (m, 3H), 1.74 (m, 2H), 1.94 (m, 2H), 3.30 (t, J=
7.3 Hz, 2H), 3.65 (m, 1H), 7.31 ppm (s, 4H); MS: m/z (%): 472 (6) [M+
]; elemental analysis calcd (%) for C28H48N4O2 (472.38): C 71.14, H
10.23, N 11.85; found: C 70.63, H 10.17, N 11.65.
2,2-Dimethyl-N-[4-(3-tetradecylureido)phenyl]propionamide (4e): This
compound was prepared as described for 4a, starting from compound 2c
(1.1 g, 7.8 mmol) and tetradecylisocyanate (2.6 mL, 9.4 mmol). The prod-
uct was purified by recrystallization from methanol. Yield 2 g of a white
powder (84%, 5.0 mmol); no melting point (decomp); Rf =0.6 (1:1
hexane/THF); 1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d=0.85 (t,
J=7.0 Hz, 3H), 1.24 (m, 22H), 1.37 (s, 9H), 1.55 (m, 2H), 2.59 (t, J=
7.8 Hz, 2H), 7.31 (d, J=8.7 Hz, 2H), 7.49 ppm (d, J=8.7 Hz, 2H); MS:
m/z (%): 431 (7) [M+]; elemental analysis calcd (%) for C26H45N3O2
(431.67): C 72.35, H 10.51, N 9.73; found: C 71.82, H 10.83, N 9.79.
1-[4-(Cyclohexylureido)phenyl]-3-octadecylurea (8c): This compound
was prepared as described for 4a, starting from compound 6 (0.93 g,
4.0 mmol) and octadecylisocyanate (1.28 g, 4.3 mmol). The product was
purified by recrystallization from DMF. Yield 1.7 g of a white powder
(81%, 3.2 mmol); m.p. >2148C (decomp); Rf =0.68 (1:1 hexane/THF);
1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d 0.85 (t, J=6.8 Hz, 3H),
1.25 (m, 35H), 1.56 (m, 3H), 1.74 (m, 2H), 1.94 (m, 2H), 3.30 (t, J=
7.3 Hz, 2H), 3.65 (m, 1H), 7.31 ppm (s, 4H); MS: m/z (%): 528 (6) [M+
]; elemental analysis calcd (%) for C32H56N4O2 (528.44): C 72.68, H
10.67, N 10.59; found: C 72.68, H 10.63, N 10.57.
1-(4-Nitrophenyl)-3-cyclohexylurea (5): This compound was prepared as
described for 4a, starting from cyclohexylamine (3,99 mL, 35 mmol) and
nitrophenyleneisocyanate (5.74 g, 35 mmol). The product was purified by
recrystallization from methanol. Yield 6.3 g of a yellow solid (71%,
1
23.9 mmol); Rf =0.6 (1:1 hexane/THF); H NMR ([D6]DMSO, 250 MHz):
d=1.49 (m, 10H), 3.48 (m, 1H), 6.31 (d, J=7.9 Hz, 1H), 7.58 (d, J=
9.0 Hz, 2H), 8.11 (d, J=9.0 Hz, 2H), 9.11 ppm (s, 1H).
1-(4-Aminophenyl)-3-cyclohexylurea (6): The nitro-compound 5 (6.3 g,
23.9 mmol) was dissolved in a mixture of THF (200 mL) and methanol
(40 mL) and Pd on activated carbon (0.6 g of 10 wt%) was added. This
mixture was stirred in an autoclave for 24 h at 408C with an H2 pressure
of 3.5 bar. The colorless mixture was filtered (Alox N) and the solvents
were evaporated. Yield 5.1 g (90%, 21.5 mmol); Rf =0.2 (1:1 hexane/
THF); 1H NMR ([D6]DMSO, 250 MHz): d=1.49 (m, 10H), 3.48 (m,
1H), 4.66 (s, 2H), 6.87 (d, J=7.9 Hz, 1H), 6.48 (d, J=8.7 Hz, 2H), 7.03
(d, J=8.7 Hz, 2H), 7.76 ppm (s, 1H); IR (Si-Wafer): n=3322, 2928, 2852,
Gelation tests: In a typical gelation test a weighed amount of the com-
pound was mixed with 2 mL of solvent in a test tube with a screw cap,
and then the mixture was heated until the solid was completely dissolved.
The resulting solution was slowly allowed to cool to room temperature.
Gelation was considered to have occurred when a homogenous substance
was obtained which exhibited no gravitational flow.
For the determination of the sol–gel transition temperature (Tgel) of the
gels the steel ball method was used.[4] A steel ball (260 mg) with a diame-
ter of 4.5 mm was placed on the top of the gel and the vial was sealed.
The samples were placed in a heating system, which was slowly heated,
typically 58CminÀ1, while the temperature was determined with a tem-
perature sensor that was dipped in a separate vial containing solvent.
The Tgel of the gel was defined as the temperature when the steel ball hit
the bottom of the vial.
1623, 1566, 1518 cmÀ1
.
N-[4-(Cyclohexylureido)phenyl]octanamide (7a): This compound was
prepared as described for 1, starting from compound 6 (0.6 g, 2.6 mmol)
and octanoyl chloride (0.54 mL, 3.0 mmol). The product was purified by
recrystallization from methanol. Yield 0.7 g of a white powder (75%,
1.9 mmol); m.p. >1928C (decomp); Rf =0.7 (1:1 hexane/THF); 1H NMR
(5:1, CDCl3, CF3COOD, 250 MHz): d=0.85 (t, J=6.8 Hz, 3H), 1.27 (m,
15H), 1.72 (m, 5H), 1.93 (m, 2H), 2.51 (t, J=8.1 Hz, 2H), 3.67 (m, 1H),
7.25 (d, J=8.7 Hz, 2H), 7.50 ppm (d, J=8.7 Hz, 2H); MS: m/z (%): 359
(25) [M+]; elemental analysis calcd (%) for C21H33N3O2 (359.26): C
70.16, H 9.25, N 11.69; found: C 69.94, H 9.12, N 11.07.
Electron microscopy: For the transmission electron microscopy a formar/
carbon-coated copper grid (300 mesh) was dipped for a very short time
(t<1 s) into the solution of the gelator in the organic solvent and put on
a weighing paper to become a gel. After 1 h the grid was placed in a
round-bottomed flask and dried at low pressure (<10À2 mbar). The grids
were examined in a Zeiss CEM 902 electron microscope, operating at
80 kV.
N-[4-(Cyclohexylureido)phenyl]tetradecanamide (7b): This compound
was prepared as described for 1, starting from compound
6 (0.5 g,
2.1 mmol) and tetradecoyl chloride (0.68 mL, 2.5 mmol). The product
was purified by recrystallization from methanol. Yield 0.95 g of a white
powder (85%, 1.8 mmol); m.p. >1988C (decomp); Rf =0.76 (1:1 hexane/
THF); 1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d=0.85 (t, 3H),
1.25 (m, 27H), 1.59 (m, 5H), 1.95 (m, 2H), 2.52 (t, J=8.1 Hz, 2H), 3.68
(m, 1H), 7.23 (d, J=8.7 Hz, 2H), 7.49 ppm (d, J=8.7 Hz, 2H); MS: m/z
(%): 443 (8) [M+]; C27H45N3O2 (443.35): C 73.09, H 10.22, N 9.47; found:
C 73.02, H 10.23, N 9.31.
Rheology: Rheological measurements were carried out with a stress rhe-
ometer Haake RS600 with a cone-plate (60 mm diameter). The width of
the gap was 0.052 mm. Oscillatory experiments were performed in a
0.001–100 Hz frequency range at constant stress in the linear regime of
deformation (1 Pa for a gel at 0.5 wt% and about 5 Pa for a gel at
2 wt%). The following procedure was used to load the sample: 1.5 mL of
solvent solution containing gelator was placed on the plate that was
about 958C and closed by a cone. The system was cooled down to 258C
at a rate of 208CminÀ1 as soon as the gap was totally filled with the gel;
the measurements were started after 30 minutes.
N-[4-(Cyclohexylureido)phenyl]octadecanamide (7c): This compound
was prepared as described for 1, starting from compound 6 (0.93 g,
4.0 mmol) and octadecoyl chloride (1.3 g, 4.3 mmol). The product was pu-
rified by recrystallization from methanol. Yield 1.7 g of a white powder
(84%, 3.4 mmol); m.p. >2008C (decomp); Rf =0.8 (1:1 hexane/THF);
1H NMR (5:1, CDCl3, CF3COOD, 250 MHz): d=0.85 (t, J=6.8 Hz, 3H),
1.25 (m, 35H), 1.73 (m, 5H), 1.95 (m, 2H), 2.52 (t, J=7.4 Hz, 2H), 3.69
Chem. Eur. J. 2005, 11, 863 – 872
www.chemeurj.org
ꢂ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
871

H.-W. Schmidt and N. Mohmeyer
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Acknowledgements
We thank the group of Professor H. Hoffmann (physicochemistry I, Uni-
versity of Bayreuth) for the assistance with rheological measurements, N.
Glaser for the electron microscopy experiments and B. Brunner (Depart-
ment of Chemical Engineering, chair of Prof. A. Jess, University of Bay-
reuth) for performing the elemental analysis. We are also indebted to
P. Schroegel and D. Kropp for their assistance in the preparation of sev-
eral compounds.
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