Liquid crystalline octopus: An alternative class of mesomorphic dendrimers

Article abstract of DOI:10.1021/ma034038i

The synthesis and the mesomorphic properties of a new series of liquid crystalline dendrimers, referred thereafter as to octopus dendrimers owing to their eight sidearms, are reported. In these dendritic systems, the arborescence is constituted of mesogen

Full text of DOI:10.1021/ma034038i

Macromolecules 2003, 36, 5593-5601
5593
Liquid Crystalline Octopus: An Alternative Class of Mesomorphic
Dendrimers
Lion el Geh r in ger , Da n iel Gu illon , a n d Ber tr a n d Don n io*
Institut de Physique et Chimie des Mate´riaux de Strasbourg, IPCMS, Groupe des Mate´riaux
Organiques, GMO, UMR 7504, CNRS/ Universite´ Louis Pasteur, 23, rue du Loess, BP 43,
F-67034 Strasbourg Cedex 2, France
Received J anuary 13, 2003; Revised Manuscript Received May 13, 2003
ABSTRACT: The synthesis and the mesomorphic properties of a new series of liquid crystalline
dendrimers, referred thereafter as to octopus dendrimers owing to their eight sidearms, are reported. In
these dendritic systems, the arborescence is constituted of mesogenic segments and aliphatic spacers,
and as such they differ quite substantially from the classical end-functionalized dendrimers whose dentritic
core is more flexible. Such a molecular design was adopted in order for the internal mesogenic segmentss
constituting the skeleton of the dendrimersto participate at every level of the molecular organization
within the mesophases. The dendritic branches, prepared by a mixed convergent/divergent method, were
attached to a tetrapodant central core to yield second generation dendrimers via amido linkage. X-ray
diffraction studies showed that the acidic dendron precursors and the final dendrimers exhibit a hexagonal
columnar mesophase, whose mesophase stability was found to depend on the number and position of the
terminal alkoxy chains. The high density of aliphatic chains imposes curved interfaces at all hierarchical
levels of the dendrimers, i.e., between the pro-mesogenic units, the aliphatic spacers, and the terminal
chains, forcing the molecules to adopt a wedgelike conformation, promoting the self-assembling toward
a supramolecular columnar organization. Because of their original molecular structure, the internal
columnar “hard” core of the columns is compatible with an onion-type structure, i.e., made up of successive,
concentric crowns occupied by aromatic and aliphatic constituents, as deduced from the analysis of the
X-ray diffraction data.
In tr od u ction
photonic, electronic, and ionic transport based-applica-
tions, depending on the functionality sought.1 Moreover,
owing to their branched nature, liquid crystal dendrim-
ers possess properties halfway between those of poly-
mers and of single monomeric species. The viscosity is
generally found to be lower than in polymers, and they
still possess important features characteristic of poly-
mers such as mesophase stabilization and good process-
ing. The first examples of reported mesomorphic den-
drimers were the so-called hyperbranched dendritic
polymers, obtained solely by random polymerization of
ABm-type anisotropic monomers having two different
functional groups (m g 2, A * B).2 Because of their
statistical mode of construction, these interesting poly-
mers are characterized by a high degree of branching
(without any cross-link) and are usually polydisperse;
i.e., the number of branches and thus the total number
of mesogenic moieties are not controlled.3 Only a few
representatives of such hyperbranched liquid crystals
have been so far synthesized, with the mesogenic units
as branching points2,4 and/or as end groups.5 Nowadays,
the field of monodisperse liquid crystal dendrimers has
properly expanded as evidenced by the development of
many new structures found compatible with the forma-
tion of various mesophases including shape-persistent,6
supramolecular,7 and end-group dendrimers.8-13
The development of new supramolecular architectures
with specific properties is a fundamental aspect of the
research in the field of molecular-based materials. Of
particular interest is the combination of precise func-
tionalities incorporated within large and well-defined
structures. Dendritic molecules or dendrimers are one
type of such new and interesting macromolecules or
oligomers that have been found suitable to overcome the
drawbacks of linear polymers.1 One of their main
originalities with respect to other high-molecular-weight
compounds is that they possess a perfectly controlled,
branched structure, a consequence of their layer-wise
construction. Dendrimers are either built outward or
inward a highly functional core species by an iterative
synthesis consisting of successive and specific elemen-
tary steps. Such sequential convergent and divergent
modes of construction lead to an almost total control of
the ultimate molecular architecture. Indeed, these
synthetic methodologies provide a high degree of control
of the molecular size and shape as well as the definite
number of functional moieties in precise locations. In
principle, these dendrimers are obtained with narrow
molecular weight distributions and without chain en-
tanglements.1
The combination of mesomorphic properties and den-
dritic structures is a new approach in the field of liquid
crystals. The interest in the construction of such mul-
tifunctional, practically monodisperse, macromolecular
objects arises from their ability to self-assemble into
mesophases and from their potential utilization as
Synthetic chemists of liquid crystalline dendrimers
have mainly concentrated their effort on the study of
the side-group systems,8-13 as schematically represented
in Figure 1asthey can be described as side-chain
dendrimers by analogy to side-chain polymers. Such
side-chain dendrimers possess a nonmesogenic, flex-
ible core with a globular nature, to the terminal
branches of which the various mesogens or pro-meso-
genic units are connected. The most commonly used
* Corresponding author: e-mail bdonnio@ipcms.u-strasbg.fr, tel
+33 388107157, fax +33 388107246.
10.1021/ma034038i CCC: $25.00 © 2003 American Chemical Society
Published on Web 06/27/2003

5594 Gehringer et al.
Macromolecules, Vol. 36, No. 15, 2003
et al. some years ago; these systems exhibited nematic
and smectic phases.16 Shibaev also foresaw the elabora-
tion of such compounds but has not yet reported on their
synthesis and physical properties.17
In this paper, the design and synthetic methodology
of novel dendrimers are reported together with their
complete analytical characterization. Such second gen-
eration dendrimers have been named octopus dendrim-
ers owing to their eight sidearms. Their thermal be-
havior and the unequivocal assignment of the meso-
phases are described, and a model accounting for the
molecular organization of these octopus dendrimers into
the columnar phases is discussed.
Syn th etic Meth od ology
F igu r e 1. Schematic 2D representation of (a) side-chain and
(b) main-chain liquid crystalline dendrimer.
Conventional end-group dendrimers, where the core
matrix is either a PAMAM, DAB, or carbosilane, are
usually built up using a divergent approach, that is,
constructed outward a central core, and the mesogenic
moieties are attached to the periphery at the final stage
of the synthesis. For the presently described dendrim-
ers, this approach appeared unsatisfactory as a number
of additional steps were required prior to synthesizing
the mesogenic moiety at each generation, before moving
up to the next generation, with the consequent dimin-
ishing overall reaction yields hampered by reactivity
and purification problems. Therefore, to improve the
reactivity of the connecting sites and to facilitate the
purification of the dendritic materials, a mixed conver-
gent/divergent synthesis was elaborated for the prepa-
ration of these dendrimers (Schemes 1-3). The consti-
tutive parts of the stilbenic branches, 4 and 7, were
prepared separately (Schemes 1 and 2) and assembled
selectively together in the next stage of the procedure
(Scheme 3). These acidic building blocks were then
coupled to a small tetra-podand core unit, functionalized
by four amino groups, to yield the final dendrimers
(Scheme 3). The anisotropic unit selected was a stilbene-
based moiety, due to both its thermal stability and the
versatility of its chemistry. Such a poorly mesogenic
segment,18 despite its anisotropy and rigidity, was also
chosen in order to test whether mesomorphism could
be induced solely by the dendrimerization process.
Recall that another family of rather different stilbene-
containing dendrimers, the so-called stilbenoid shape-
persistent dendrimers, has been reported by Meier and
Lehmann6c-e to show mesomorphism.
dendritic cores are polypropyleneimines (DAB),8 poly-
amidoamines (PAMAM),9 polysiloxanes,10 and polycar-
bosilanes.11 Induction of liquid crystalline properties
was achieved either by grafting classical calamitic
mesogens such as alkylcyanobiphenyl, cholesteryl, or
phenyl benzoate derivatives or by connecting nonme-
sogenic groups such as perfluoroalkyl chains12 or poly-
alkylated benzoate moieties.13 In general, the choice of
the chemical structure of the terminal units grafted at
the periphery of the macromolecules appeared crucial
to determine the nature of the mesomorphism of the
entire compound, the treelike scaffolding being con-
strained into a limited number of conformations. In the
former examples, smectic phases were observed as for
the monomeric parents, while columnar phases were
induced for the polyalkoxy benzoate systems. These
latter examples also prove the importance of microphase
separation in stabilizing or inducing mesomorphism
since perfluoroalkyl and polyalkoxy benzoates are not
mesomorphic themselves. The chemical incompatibility
between the flexible dendritic core and the functional-
ized terminal groups leads to AB-block structures14 and
enhances microphase separation at a molecular level
and helps to stabilize further smectic and/or columnar
supramolecular arrangements.15 The mesophase stabil-
ity therefore depends on the degree of amphiphilicity
and on the core conformation (enthalpy/entropy bal-
ance) as well as on the judicious choice of the mesogenic
units.
Regarding the dendrimers studied here, the branch-
ing points are no longer single atoms (C, N, Si) but
consist of rigid and anisotropic molecular moieties
instead, these units being linked together through long
and flexible alkyl spacers (Figure 1b). Large anisotropic
groups are now present at every level of the dendritic
hierarchy, and the dendrimers will be forced to adopt
constrained and regular structures. As such, the ani-
sometric branches will not radiate isotropically as in
side-chain dendrimers, but on the contrary will prefer-
entially favor an anisotropic order by a gain in the en-
thalpy of the system in order to produce the most stable
structure. Consequently, complementary or/and coop-
erative effects such as the amplification of the properties
are expected to occur. Such main-chain dendrimers may
represent an interesting alternative for the development
of original molecular materials having a new architec-
ture (Figure 1b) and maybe new ways to self-organize
into mesophases. As far as we are aware, the most
closely related compounds being previously reported are
the so-called willow dendrimers synthesized by Percec
Both the internal and terminal constitutive parts of
the dendritic branches were prepared using standard
chemical reactions, starting from the commercially
available 3,5-dimethoxybenzaldehyde for the internal
branch and 4-hydroxybenzaldehyde, 3,4-dihydroxyben-
zaldehyde, 3,5-dihydroxybenzyl alcohol, and 3,4,5-tri-
hydroxymethyl benzoate for the construction of the
peripheral mesogenic units.
The internal branching unit, 4, was prepared in
several steps as shown in Scheme 1. The starting
material, 3,5-dimethoxy benzaldehyde, was quantita-
tively converted into the corresponding styrene com-
pound (1) by a Wittig reaction. The coupling of this
styrene derivative with the appropriate ethyl 4-iodo-
benzoate via a palladium-catalyzed Heck reaction then
produced the dimethoxystilbene ester derivative, 2, in
good yields. The dihydroxy compound 3 was obtained
in two successive steps including first the demethylation
with BBr3, immediately followed by the in-situ rees-
terification of the acid function since the ester group

Macromolecules, Vol. 36, No. 15, 2003
Liquid Crystalline Octopus 5595
Sch em e 1. P r ep a r a tion of th e In ter n a l Br a n ch in g Un it 4
Sch em e 2. P r ep a r a tion of th e Ter m in a l Gr ou p s 7a -d
did not survive the demethylation. Finally, bromoun-
troscopy. In all cases, the results were in good agree-
ment with the proposed structures.
decanol was grafted to the free hydroxy groups of 3 by
a Mitsunobu etherification to yield the prefunctionalized
internal core moiety, 4.
Resu lts
The various mono-, di-, and trialkoxystilbenoid-like
moieties, 7a -d , were all prepared by identical synthetic
sequences, including the prior quantitative conversion
of the appropriate alkoxy-substituted benzaldehydes
(5a -d ) into the corresponding styrenes (6a -d ), followed
in a second step by the coupling with iodophenol by a
palladium-catalyzed Heck reaction (Scheme 2). The
overall reaction yields were dependent on the substitu-
tion pattern.
The compounds discussed in this study are schemati-
cally represented in Scheme 3. In the present work,
stabilization and/or induction of the mesomorphic prop-
erties, when compared to the thermal behavior of the
low-molar-weight monomeric precursors, was observed
upon the incorporation of the nonmesogenic stilbene
moieties within the arborescent scaffolding according
to 10a -c, yielding a new family of high-molar-weight
liquid crystalline dendrimers.
The esters, precursors of the acidic stilbenic moieties
8, were obtained by a straightforward double alkylation
between the internal unit 4 and the appropriate stil-
benoide derivative (7a -d ); their subsequent hydrolysis
yielded the acid monodendrons 8a -d (Scheme 3). The
targeted second generation dendrimers (10a -c) were
obtained by the amidation reaction of the acid mono-
dendrons with the tetraamino core N,N,N′,N′-tetrakis-
(3-aminopropyl)-1,4-butanediamine (DAB; Generation
1.0). For the reaction to proceed more efficiently, it was
necessary to preliminarily activate the acid function of
the monodendrons by diphenyl(2,3-dihydro-2-thioxo-3-
benzoxazolyl)phosphonate, 9.19 Unfortunately, the den-
drimer 10d could not be prepared due to the complete
insolubility of 8d in organic solvents.
All the final compounds were isolated as either air-
stable waxy solids (8a , 10a ), crystalline materials (8b,
8d , 10b), or viscous oils (8c, 10c) and were soluble in
most organic solvents, except 8d . The acidic stilbenic
arms were purified by repeated crystallizations in
petroleum ether and the dendrimers by flash chroma-
tography. Compounds 8 and 10 were characterized by
elemental analysis, 1H and 13C NMR spectroscopy, and
the final dendrimers by additional MALDI-TOF spec-
The thermal behavior of the acidic moieties and of the
dendrimers was examined by three complementary
techniques: polarized-light optical microscopy (POM),
differential scanning calorimetry (DSC), and X-ray
diffraction (XRD).
P OM Exp er im en ts. The liquid crystalline behavior
of the acids 8a ,c and of the three dendrimers 10a -c
was first evidenced by the observation of large and
homogeneous fluid domains, which coalesced on increas-
ing the temperature further; in contrast, 8b and 8d were
found to melt directly into the isotropic liquid at 146
and 193 °C, respectively, without showing any me-
sophase. No obvious and recognizable optical texture
could be observed under the polarized microscope,
except for dendrimer 10b for which a texture displaying
rather large cylindrical domains was observed (Figure
2); such defects are usually characteristic of a columnar
phase. The two acids, 8a and 8c, appeared liquid
crystalline at room temperature, with the mesophase
stability decreasing in accordance with the reduction of
the number of terminal aliphatic chains. The corre-
sponding dendrimers, 10a and 10c, were also found to
be mesomorphic near the ambient and with again an

5596 Gehringer et al.
Macromolecules, Vol. 36, No. 15, 2003
Sch em e 3. P r ep a r a tion of th e Stilben ic Br a n ch es (Acid s 8a -d ) a n d Octop u s Den d r im er s 10a -c
important decrease of the mesophase-to-isotropic liquid
transition temperature on going from 10a to 10c.
Notwithstanding, whereas the acid 8b was devoid of
mesomorphism, a mesophase was induced for the den-
drimer 10b, which existed at much higher temperatures
than that of 10a or 10c, but over a narrower tempera-
ture range. Note that the ester compounds, precursors
of 8a -d , were not liquid crystalline either.
Optical microscopy was thus not a conclusive tech-
nique in giving an unequivocal mesophase assignment
but was nevertheless sufficient to prove induction of
mesomorphism by dendrimerization.
DSC Mea su r em en ts. Confirming the results of the
microscopic observations, several transitions likely as-
sociated with a liquid crystalline behavior were detected
by DSC. The acidic branches (8a , 8c) and the dendrim-
ers (10a -c) exhibited complicated DSC traces during
the first heating scan. However, on subsequent heat-
ing-cooling cycles, more simple and reproducible ther-
mograms were obtained, an indication of the good
thermal stability of the compounds. The traces consisted
of either a glass- or crystal-to-mesophase transition and
a mesophase-to-isotropic liquid transition (Figure 3).
The transition temperatures of the acids and dendrim-
ers are gathered in Table 1.
X-r a y Diffr a ction Stu d ies. Temperature-dependent
X-ray diffraction experiments were systematically car-
ried out in order to identify unequivocally the nature
of the mesophases. Qualitatively similar X-ray patterns
were obtained for all the acidic branches and dendrim-
ers, whatever the number and the position of the
peripheral aliphatic chains, and confirmed the existence
of liquid crystalline mesophases. The X-ray patterns
consisted of a diffuse scattering halo in the wide-angle
region, centered around 4.5 Å, corresponding to the
liquidlike order of the molten aliphatic chains. In the

Macromolecules, Vol. 36, No. 15, 2003
Liquid Crystalline Octopus 5597
tion with the anisotropic blocks lying more or less in
planes perpendicular to the columnar axis, rather than
a prolate conformation (cylindrical) within the columns.9b
However, the small discrepancy between the estimated
molecular diameters (110-120 Å) and the measured
lattice parameters (85-95 Å) of the Colh mesophases,
corresponding to a molecular contraction of about 10-
20%, can only be partly attributed to the liquidlike state
of the molten aliphatic chains which cannot account for
more than a few percent only. This thus indicates that
the small rigid segments have to be tilted with respect
to the columnar axis, i.e., the stilbene groups are not
contained in the hexagonal plane, and/or the orientation
within the plane perpendicular to the columnar axis of
their long molecular axis is nonradial, i.e. there is no
preferential direction of the molecular axes of the
stilbene units in this plane.
F igu r e 2. Optical texture of 10b at 100 °C.
To propose a possible molecular arrangement of these
compounds within the columns, the number of octopus
able to fill a columnar slice 4.5 Å thick was first
calculated. This distance corresponds to the average
liquidlike correlations between the mesogens in a liquid
crystalline phase and has recently been justified by a
simple geometrical model for some other liquid crystal-
line dendrimers.9b Let us remark that in nondiscoid
systems a columnar slice does not have a particular
significant meaning, and it does not necessarily imply
that in the present case the columns result from the
stacking of flat dendrimeric or supramolecular dendritic
disks on top of each other (vide infra), as in purely
discotic materials. However, this approach permits the
calculation of a linear density along the columnar axis
and a comparison with other low-molecular-weight
liquid crystalline materials forming columnar struc-
tures. Thus, the molecular volumes, VM, were estimated
considering a density of 1 g cm-3 for the molecules in
the mesophase and corrected by a temperature factor.20
Such a value for the density of dendrimers in the
mesomorphic state is totally acceptable, and similar
densities have been measured in side-chain dendrimers
without changing from the first generation to the fifth.9c
The volume of one columnar slice 4.5 Å thick thus equals
Sh, where S is the columnar cross section (Table 1) and
h the thickness of the slice. The number of molecules
per slice can thus be directly obtained by N ) hS/ VM.
It showed that while two dendrimers 10a are necessary
to fill such a slice, three dendrimers 10b are needed.
On average, this corresponds to about 48 aliphatic
chains that radiate out of the interface of such defined
cylindrical slice. Interestingly, for 10c, one isomeric
compound of 10b, which can be regarded as a structural
intermediate of 10a and 10b, the number of molecules
satisfying these conditions is reduced, and N ) 2.5, i.e.,
with only 40 radiating aliphatic chains. This may
explain the smaller phase stability of the latter with
respect to the more densely packed dendrimers. Such a
substitution pattern (in the 3,5-position of the terminal
aromatic ring) has often been found incompatible with
mesophase formation and/or broad mesomorphic tem-
perature ranges. This result has been verified many
times, particularly in polycatenar liquid crystals,21
showing the importance of an aliphatic chain in the para
position in promoting and stabilizing mesomorphism.
Thus, since more than one molecule is necessary to
circumvent the dimension of the columns, the formation
of the mesophase likely results from a self-assembling
process of octopus molecules having a wedgelike con-
F igu r e 3. DSC thermogram of 10b.
small-angle region, two and up to five sharp reflections
(10b, Figure 4) were observed, with the reciprocal
x
x
x
x
spacings in the ratios 1, 3, 4, 7, and 12, which
were indexed as (hk) ) (10), (11), (20), (21), and (22);
these reflections are in agreement with a 2D hexagonal
lattice. The results of these investigations are sum-
marized in Table 1. The X-ray pattern of one represen-
tative is shown in Figure 4.
Discu ssion
All the new compounds synthesized, with the excep-
tion of the two acidic branches (8b, 8d ), are mesomor-
phic, self-assembling into a hexagonal columnar me-
sophase. The nature of the mesophase was by all means
expected due to the mismatch between the aromatic
surface areas and that of the aliphatic ones, resulting
in the curvature of the interfaces and hence to columnar
mesophases. These results are indeed in agreement with
other findings7,13 and with some of our previous work
on side-chain dendrimers for which the increasing
number of peripheral chains grafted per terminal groups
was associated with a change of morphology from
lamellar to columnar structures.9b,c As far as the den-
drimers 10a -c are concerned, the parameters of the
hexagonal lattices, a, are in overall good agreement with
the molecular dimensions estimated by molecular dy-
namics simulation; the diameters of the dendrimers in
their most extended flat conformation were found to
vary between 110 and 120 Å. For such a simulation, the
aliphatic chains (terminal and internal) were considered
in their liquidlike conformation, i.e., with some amount
of gauche conformations. This similarity suggests that
the octopus dendrimers preferably adopt an oblate
shape that is a flat extended or a wedgelike conforma-

5598 Gehringer et al.
Macromolecules, Vol. 36, No. 15, 2003
Ta ble 1. Th er m a l Beh a vior a n d X-r a y Ch a r a cter iza tion of th e Den d r itic Br a n ch es a n d Octop u s Den d r im er sa
indexation
compd
transition temperature/°C
Colh 52 (15.5b) I
d
meas/Å
I
hk
dcalc/Å
mesophase parameters
N
8a
64.5
37.5
24.4
4.5
VS
S
S
10
11
21
h
64.7
37.35
24.45
T ) 30 °C
6.3
a ) 74.7 Å
S ) 4830 Å2
Vcell ) 21 750 Å3
br
8b
8c
Cr 146 I
g -35 (0.1c) Colh 28 (16.7b) I
55.2
31.7
27.05
20.8
4.5
VS
S
M
S
10
11
20
21
h
54.8
31.6
27.4
20.7
T ) 25 °C
5.6
a ) 63.3 Å
S ) 3470 Å2
Vcell ) 15 600 Å3
br
8d
10a
Cr 193 I
Cr -3 (95.6b) Colh 84 (17.8b) I
77.0
44.5
4.5
VS
S
br
10
11
h
77.0
44.45
T ) 60 °C
2.1
2.9
a ) 88.9 Å
S ) 6850 Å2
Vcell ) 30 810 Å3
T ) 100 °C
10b
10c
Cr 95 (227b) Colh 132 (17.8b) I
82.45
47.55
41.4
31.1
23.8
4.5
75.5
43.0
28.5
4.5
VS
S
M
S
M
br
VS
S
10
11
20
21
22
h
10
11
21
h
82.45
47.6
41.2
31.15
23.8
a ) 95.2 Å
S ) 7850 Å2
Vcell ) 35 320 Å3
g -25 (0.1c) Colh 42 (17.5b) I
75.1
43.3
28.4
T ) 30 °C
2.5
a ) 86.7 Å
S
br
S ) 6510 Å2
Vcell ) 29 300 Å3
a
Detailed indexation at a given temperature (T) [dmeas and dcalc are the measured and calculated diffraction spacings ( d10 ) (1/
N
hk)[∑hkdhk(h2 + k2 + hk)1/2], where Nhk is the number of hk reflections); I is the intensity of the diffraction signal (VS ) very strong, S
) strong, M ) medium, br ) broad); hk is the indexation of the two-dimensional lattice; a is the lattice parameter (a ) (2/x3) d10 ), S is
b
the lattice area (S ) a d10 ), Vcell is the volume of the hexagonal cell (hS)]. N ) number of molecules per slice of columns hS. ∆H (kJ
mol-1). c ∆Cp (kJ mol-1 K-1).
F igu r e 4. X-ray pattern of 10b at 100 °C.
F igu r e 5. Schematic representation of the self-assembling
and self-organization processes of the octopus in the Colh phase
with (a) bent and (b) tilted conformations.
formation into supramolecular columns, the latter fur-
ther self-organizing into a 2D hexagonal lattice.
On the basis of these results, a simple model account-
ing for the organization of these dendrimers in the
mesophase can be proposed. Considering both the
diblock chemical nature of these octopus and the simi-
larity between the molecular dimensions and intercco-
lumnar distances, an onion structure for the columns
is most likely probable. As seen above, to satisfy the
parameters determined by X-ray diffraction, the mol-
ecules must adopt a nearly flat conformation. However,
the liquidlike order of the chains does not by itself
explain the slight contraction of the cell with respect to
the molecular diameters. Clearly, the overall molecular
conformation of the dendrimer in the mesophase is
driven by the steric congestion of the terminal aliphatic
chains and depends on the segregation between the
different constitutive blocks. Indeed, to compensate
molecular areas at the various interfaces at every level
of the arborescence, the internal and external rigid
segments have to be tilted. This arrangement may be
additionally further stabilized by inter-mesogen interac-
tions. To do so, the constitutive anisotropic segments
may deviate from the radial direction within a plane
perpendicular to the columnar axis (Figure 5a). How-
ever, such a unique arrangement would be energetically
unfavorable because of the strong elastic energy in-
volved and to the small stabilizing enthalpy due to the
nonoptimized inter-mesogen contacts in the plane per-
pendicular to the columnar axis. One can also consider
that these segments are tilted with respect to the
columnar axis, each mesogenic subunit belonging to the
same level of the dendrimer hierarchy not necessarily
lying in the same plane (Figure 5b). As such, the
dendrimeric supramolecular association would be more
stabilized due to the enhancement of the inter-mesogen
interactions and to the consequent gain in enthalpy.

Macromolecules, Vol. 36, No. 15, 2003
Liquid Crystalline Octopus 5599
However, the packing would not be optimized along the
stacking direction, since the segment could point up and
down the axis. Clearly, these systems are not static and
molecular diffusion does take place; all the conforma-
tional possibilities lying between these two extreme
structures may occur, with the aim to tend preferen-
tially toward the model with the most stable molecular
conformation. As observed by Percec et al.,7 columnar
structures are obtained from the self-assembling of the
most stable molecular conformation having either a
wedgelike or conical-like shape. In the case of the
octopus dendrimers, and on the basis of our X-ray
results, the most probable molecular shape is that of a
wedge (Figure 5), which self-assemble together into
columns (Figure 5).
and to the construction of heterolithic systems (i.e.,
several different anisotropic bricks). Since the disposi-
tion of the mesogenic species forming the dendritic
matrix is perfectly controlled, it is possible to consider
a range of novel morphologies to be formed. For in-
stance, it is possible to envisage segmented “block-type”
dendrimers, where the two halves of the dendrimer
contain different mesogenic units. Alternatively, alter-
nated dendrimers can be built in which the branching
mesogenic unit is different at each generation. Such
dendrimers and co-dendrimers are currently under
investigation and will be reported in due course.
Exp er im en ta l a n d Meth od of Ch a r a cter iza tion
1
Tech n iqu es. H and 13C NMR spectra were recorded on a
Regarding the precursor acid monodendrons, the fact
that the same mesophase was observed, with dimen-
sions of the same order of magnitude, strongly supports
that the dendrimers and the monodendrons are simi-
larly organized and that the former likely adopt wedge-
like shapes. It was found that on average six dendritic
branches like 8a and 8c22 were necessary to satisfy the
space-filling requirements of a slice 4.5 Å thick. The
smaller number of monodendrons, at first expected, able
to fill such slices is due to the substantial reduction of
the lattice parameters compared to those of the octopus,
clearly in connection to the absence of the central DAB
core moiety. As the supramolecular dendrimers de-
scribed by Percec et al.,7 the acids adopt also a wedge
shape and likely self-assemble into supramolecular
associations that are stabilized further by H-bonding
interactions due to the focal free acid function. More-
over, since they benefit from more degrees of freedom,
they are not as densely packed and not as constrained
to occupy the available volume than the corresponding
dendrimers. These supermolecules can also adopt other
conformations as well as exchange their positions in the
transverse direction to the columnar axis and along this
axis. For these dendritic acids, the wedge shape is
stabilized by the incompatibility of the different molec-
ular blocks, the large number of terminal chains, and
the ability to form intermolecular hydrogen bonds when
assembled into columns.
Bruker AC200 spectrometer in CDCl3 or d6-THF solutions.
MALDI-TOF spectra were recorded on a Bruker biflex III
spectrometer in a dithranol matrix (1,8,9-anthracenetriol). The
optical textures of the mesophases were studied with a Nikon
polarizing microscope equipped with a Mettler FP8 hot stage
and an FP80 central processor. The transition temperatures
and enthalpies were measured by differential scanning calo-
rimetry with a Perkin-Elmer DSC-7 instrument operated at
a scanning rate of 10 °C min-1 on heating. The apparatus was
calibrated with indium (156.6 °C, 28.4 J g-1) and gallium (29.8
°C) as the standards. The XRD patterns were obtained with
three different experimental setups. In all cases, a linear
monochromatic Cu KR1 beam (λ ) 1.5405 Å) was obtained
using a sealed-tube generator (900 W) equipped with a bent
quartz monochromator. In the first set, the transmission
Guinier geometry was used, whereas a Debye-Scherrer-like
and a flat film geometry were used in the second and third
experimental setups, respectively. In all cases, the crude
powder was filled in Lindemann capillaries of 1 mm diameter.
An initial set of diffraction patterns was recorded on an image
plate; periodicities up to 80 Å can be measured, and the sample
temperature was controlled to within (0.3 °C. The second set
of diffraction patterns was recorded with a curved Inel CPS
120 counter gas-filled detector linked to a data acquisition
computer; periodicities up to 60 Å can be measured, and the
sample temperature was controlled to within (0.05 °C. Finally,
the last set of diffraction patterns was recorded on image plate,
and periodicities up to 350 Å can be measured, and the sample
temperature was controlled to within (0.01 °C. In each case,
exposure times were varied from 1 to 24 h depending on the
specific reflections being sought (weaker reflections obviously
taking longer exposure times).
Con clu sion s
Gen er a l P r oced u r es. Preparation of Internal Branch (4).
(1) A solution of 3,5-dimethoxybenzaldehyde (11.77 g, 0.07
mol), methyltriphenylphosphonium bromide (27.8 g, 0.078
mol), and t-BuOK (8.74 g, 0.078 mol) in dry THF (100 mL)
was stirred for 2 h at room temperature under argon. Then,
the reaction was quenched by adding 10 mL of a saturated
aqueous solution of NH4Cl. The solvents were removed under
vacuum. The crude product was extracted with CH2Cl2, and
the organic layer was washed with water and dried over
MgSO4, and the solvent was evaporated. Pure 1 was isolated
by column chromatography on silica gel (eluent petroleum
Several novel liquid crystalline dendrimers have been
synthesized, containing stilbene groups as the basic
elementary constitutive rigid-rod-like subunits. They
were obtained by a mixed divergent-convergent method,
consisting of the preparation of the acid branches and
their subsequent grafting onto a multibranched central
core through an amido linkage. They showed a Colh
mesophase, with various temperature ranges, the tran-
sition temperatures and mesophase stability being
influenced by the substitution pattern of the terminal
branches. Preliminary calculations suggest that these
dendrimers self-arranged into onion-type columns, though
this model should be confirmed further by extending
this study to provide a more comprehensive structural
characterization. Moreover, the preparations of higher
generation dendrimers are currently being carried out
in order to study the influence of the generation number
on the mesomorphic properties.
1
ether-CH2Cl2: 7-3) as a colorless oil (10.2 g, 90%). H NMR
(CDCl3): δ 6.66 (dd, 1H, J ) 10.8 and 17.1 Hz), 6.58 (d, 2H, J
) 2.35 Hz), 6.4 (t, 1H, J ) 2.35 Hz), 5.74 (d, 1H, J ) 17.1 Hz),
5.26 (d, 1H, J ) 10.8 Hz), 3.82 (s, 6H).
(2) A solution of 1 (10 g, 0.06 mol), Pd(OAc)2 (0.54 g, 2.4
mmol), tri(o-tolyl)phosphine (ToP, 1.1 g, 3.6 mmol), and
4-iodoethylbenzyl ester (15.3 g, 0.055 mol) in dry NEt3 (100
mL) was stirred for 2 h at 60 °C under argon. Then the mixture
was stirred for 1 day at 80 °C. After the reaction was complete,
the solvent was evaporated. The crude product was dissolved
in CH2Cl2 and washed with water and dried over MgSO4, and
the solvent was evaporated. The crude product was purified
by column chromatography on silica gel (eluent petroleum
These optimistic results offer many opportunities in
the design of a wide range of new systems of this type.
In fact, this concept can be extended to other homolithic
systems (i.e., one type of elementary anisometric brick)
ether-CH2Cl2: 3-7) to obtain
a yellow solid which was
crystallized from hexane to yield pure 2 (14 g, 80%) as a white

5600 Gehringer et al.
Macromolecules, Vol. 36, No. 15, 2003
solid. 1H NMR (CDCl3): δ 8.04 (d, 2H, J ) 8.3 Hz), 7.56 (d,
2H, J ) 8.3 Hz), 7.14 (s, 2H), 6.70 (d, 2H, J ) 2. 2 Hz), 6.44 (t,
1H, J ) 2.2 Hz), 4.39 (q, 2H, J ) 7.1 Hz), 3.85 (s, 6H), 1.41 (t,
3H, J ) 7.1 Hz).
(m, 4H), 1.27 (m, 36H), 0.89 (t, 6H, J ) 6.7 Hz). 7d : 40%,
1
white solid. H NMR (CDCl3): δ 7.40 (m, 4H), 6.87 (m, 10H),
3.97 (t, 2H, J ) 6.3 Hz), 1.79 (m, 2H), 1.27 (m, 18H), 0.89 (t,
3H, J ) 6.7 Hz).
(3) 2 (6 g, 0.019 mol) was dissolved in CH2Cl2 (100 mL). The
solution was cooled at -40 °C, and BBr3 (96 mL, 0.096 mmol)
was added dropwise. Then, the mixture was warmed to room
temperature for 1 day. The mixture was poured onto an ice
bath, and the solvents were removed under reduce pressure.
The crude product was dissolved in MeOH (100 mL) and
H2SO4 (5 mL). The mixture was refluxed overnight, and then
the solvent was removed in vacuo. The crude product was
dissolved in ethyl acetate, washed with a saturated aqueous
solution of NaHCO3, dried over MgSO4, and then concentrated
in a vacuum. Pure 3 (3.3 g, 65%) was obtain by precipitation
in petroleum ether as a yellow solid. 1H NMR (CD3OD): δ 8.04
(d, 2H, J ) 8.3 Hz), 7.66 (d, 2H, J ) 8.3 Hz), 7.18 (d, 2H, J )
3.4 Hz) 6.60 (s, 2H), 6.3 (s, 1H), 3.03 (s, 3H).
Preparation of the Acidic Branches (8a -d ). A solution of the
appropriate phenol derivative 7 (2.4 equiv), compound 4 (1
equiv), and K2CO3 (10 equiv) in DMF (c ) 0.05 mol/L) was
stirred for 2 days at 80 °C. Then, the solvent was evaporated
under reduce pressure. The crude product was extracted with
CH2Cl2, and the organic layer was washed with a saturated
aqueous solution of NH4Cl, dried over MgSO4, concentrated
in vacuo, and purified by column chromatography on silica gel
(eluent CH2Cl2-petroleum ether: 7-3) to give a yellow viscous
oil. Then, this oil was solubilized in THF (c ) 0.02 mol/L) and
added to an aqueous solution of KOH (40 equiv). The mixture
was refluxed to complete reaction and precipitated in
a
aqueous solution of HCl (10%). The acid 8 was then filtrated,
washed with water and dried under reduce pressure, and
purified by crystallization in petroleum ether. 8a : 60%,
colorless waxy solid. 1H NMR (CD2Cl2): δ 8.09 (d, 2H, J ) 8.5
Hz), 7.58 (d, 2H, J ) 8.5 Hz), 7.42 (d, 4H, J ) 8.8 Hz), 7.14 (s,
2H), 6.88 (m, 8H), 6.69 (s, 6H), 6.44 (s, 1H), 4.01 (m, 20H),
1.79 (m, 20H), 1.37 (m, 136), 0.89 (t, 18H, J ) 6.9 Hz). 13C
NMR (CDCl3): δ 160.6, 158.8, 153.3, 142.6, 138.5, 138.0, 132.9,
131.8, 130.7, 130.0, 127.7, 127.5, 127.3, 126.7, 126.4, 114.7,
105.4, 105.0, 73.5, 69.2, 68.1, 31.9, 30.4, 29.7, 29.6, 29.4, 29.3,
26.1, 22.7, 14.1. Anal. Calcd for C137H219O12: C, 79.91%; H,
10.77%; O, 9.32%. Found: C, 79.97%; H, 10.87%; O, 9.13%.
(4) 3 (1.6 g, 5.58 mmol), 1-bromoundecanol (3.1 g, 0.012 mol),
and triphenylphosphine (2.66 g, 0.012 mol) were dissolved in
dry THF (50 mL) under argon. The solution was then cooled
to 0 °C, and diisopropyl azodicarboxylate (DIAD, 2.3 mL, 0.012
mol) was added dropwise. After complete addition, the mixture
was refluxed overnight. The solvent was removed, and the
crude product was purified by column chromatography on
silica gel (eluent petroleum ether-CH2Cl2: 3-7) to give 4 (2.5
1
g, 60%) as a yellow oil. H NMR (CDCl3): δ 8.03 (d, 2H, J )
8.3 Hz), 7.55 (d, 2H, J ) 8.3 Hz), 7.12 (s, 2H), 6.67 (s, 2H),
6.42 (s, 1H), 3.98 (t, 4H, J ) 6.6 Hz), 3.93 (s, 3H), 3.42 (t, 4H,
J ) 6.8 Hz), 1.83 (m, 8H), 1.4 (m, 36H).
MALDI-TOF MS: molecular weight calcd for C137H219O12
:
m/z: 2057.2. Found: m/z: 2057.7. 8b: 70%, white solid. 1H
NMR (CD2Cl2): δ 8.05 (d, 2H, J ) 8.2 Hz), 7.55 (d, 2H, J )
8.2 Hz), 7.40 (d, 4H, J ) 8.8 Hz), 6.97 (m, 16H), 6.67 (s, 2H),
6.43 (s, 1H), 3.99 (m, 16H), 1.81 (m,16H), 1.27 (m, 100H), 0.89
(t, 12H, J ) 6.6 Hz). 13C NMR (CDCl3): δ 160.5, 158.6, 149.2,
148.8, 130.9, 130.6, 130.2, 127.4, 126.4, 126.3, 119.6, 114.6,
113.8, 111.4, 105.4, 69.3, 68.0, 31.9, 29.6, 29.5, 29.4, 29.3, 26.0,
22.7, 14.1. Anal. Calcd for C113H172O10: C, 80.28%; H, 10.25%;
Found: C, 80.17%; H, 10.28%. MALDI-TOF MS: molecular
weight calcd for C113H172O10: m/z: 1689.6. Found: m/z: 1690.3.
8c: 80%, colorless viscous oil. 1H NMR (CD2Cl2): δ 8.09 (d,
2H, J ) 8.2 Hz), 7.58 (d, 2H, J ) 8.2 Hz), 7.42 (d, 4H, J ) 8.8
Hz), 6.84 (m, 19H), 3.96 (m, 16H), 1.79 (m, 16H), 1.27 (m,
100H), 0.89 (t, 12H, J ) 6.7 Hz). 13C NMR (CDCl3): δ 160.6,
160.5, 158.9, 142.5, 139.6, 138.5, 130.7, 129.8, 128.6, 127.7,
126.6, 126.4, 114.7, 114.0, 107.1, 105.4, 104.8, 100.5, 68.1, 31.9,
29.6, 29.4, 29.3, 29.2, 26.1, 22.7, 14.1. Anal. Calcd for
Preparation of the Terminal Branches (7a -d ).
(6a -d ) A solution of the appropriate aldehyde 5a -d (1
equiv), methyltriphenylphosphonium bromide (1.1 equiv), and
t-BuOK (1.1 equiv) in dry THF (c ) 0.5 mol/L) was stirred for
2 h at room temperature under argon. Then, the reaction was
quenched by adding a small amount of a saturated aqueous
solution of NH4Cl. The solvents were removed under vacuum.
The crude product was extracted with CH2Cl2, and the organic
layer was washed with water and dried over MgSO4 and the
solvent evaporated. Pure vinyl compound (6a -d ) was isolated
by column chromatography on silica gel (eluent petroleum
ether-CH2Cl2: 7-3). 6a : 93%, white solid. 1H NMR (CDCl3):
δ 6.61 (m, 3H), 5.62 (d, 1H, J ) 17.6 Hz), 5.17 (d, 1H, J ) 10.9
Hz), 3.97 (m, 6H), 1.78 (m, 6H), 1.27 (m, 54H), 0.89 (t, 9H, J
1
) 6.7 Hz). 6b: 85%, white solid. H NMR (CDCl3): δ 6.90 (m,
3H), 6.64 (dd, 1H, J ) 10.9 Hz and J ) 17.6 Hz), 5.60 (d, 1H,
J ) 17.6 Hz), 5.13 (d, 1H, J ) 10.9 Hz), 4.01 (m, 4 H), 1.82 (m,
4H), 1.27 (m, 36H), 0.89 (t, 6H, J ) 6.7 Hz). 6c: 95%, white
C
113H172O10: C, 80.28%; H, 10.25%; O, 9.46%. Found: C,
79.26%; H, 10.20%; O, 9.39%. MALDI-TOF MS: molecular
1
solid. H NMR (CDCl3): δ 6.64 (dd, 1H, J ) 10.9 Hz and J )
weight calcd for C113H172O10: m/z: 1689.6. Found: m/z: 1689.5.
1
17.6 Hz), 6.55 (d, 2H, J ) 2.4 Hz), 5.71 (d, 1H, J ) 17.6 Hz),
5.23 (d, 1H, J ) 10.9 Hz), 3.95 (t, 4H, J ) 6.5 Hz), 1.74 (m,
4H), 1.28 (m, 36H), 0.89 (t, 6H, J ) 6.7 Hz). 6d : 90%, white
solid. 1H NMR (CDCl3): δ 7.34 (d, 2H, J ) 8.7 Hz), 6.87 (d,
2H, J ) 8.7 Hz), 6.67 (dd, 1H, J ) 17.6 Hz and J ) 10.9 Hz),
5.61 (d, 1H, J ) 17.6 Hz), 5.13 (d, 1H, J ) 10.9 Hz), 3.97 (t,
2H, J ) 6.5 Hz), 1.78 (m, 2H), 1.28 (m, 18H), 0.89 (t, 3H, J )
6.7 Hz).
8d : 70%, white solid. H NMR (CDCl3): δ 8.07 (m, 2H), 7.60
(m, 2H), 7.42 (m,4H), 7.13 (m, 2H), 6.88 (m, 16H), 6.68 (m,
2H), 6.44 (s, 1H), 4.01 (m, 12H), 1.79 (m, 12H), 1.37 (m, 64H),
0.89 (t, 6H).
Procedure for the Octopus Dendrimers (10a -c). To a solution
containing the monodendron acid 8a -c (4.8 equiv), condensing
agent 9 (5.28 equiv), and NEt3 (4.8 equiv) in 1-methyl-2-
pyrrolydinone (NMP, c ) 0.1 mol/L) was added a solution of
DAB-G1 (1 equiv) in NMP (c ) 0.02 mol/L). The solution was
stirred at room temperature (8a , 8c) or at 60 °C (8b) for 2
days and then poured into 5% aqueous NaHCO3. The precipi-
tate was filtered out and purified by column chromatography
on alumina gel (eluent CH2Cl2-MeOH: 99-1) to give the
desired pure dendrimer 10a -c. 10a : 40%, colorless waxy solid.
1H NMR (CD2Cl2): δ 7.76 (d, 8H, J ) 7.9 Hz), 7.48 (d, 8H, J
) 8.2 Hz), 7.40 (d, 16H, J ) 8.8 Hz), 6.95 (m, 68H), 6.37 (s,
4H), 3.95 (m, 80H), 3.46 (m, 8H), 2.47 (m, 12H), 1.77 (m, 80H)
1.45 (m, 556H), 0.88 (t, 72H, J ) 6.9 Hz). 13C NMR (CDCl3):
δ 167.1, 161.0, 159.3, 153.7, 140.4, 139.1, 138.1, 134.0, 133.2,
130.9, 130.3, 128.1, 127.8, 127.5, 126.8, 115.0, 105.5, 104.8,
101.6, 73.8, 69.3, 68.5, 32.3, 30.7, 30.1, 30.0, 29.8, 29.7, 26.5,
26.4, 23.1, 14.3. Anal. Calcd for C564H908N6O44: C, 79.87%; H,
10.84%; N, 0.99%; O, 9.3%, Found: C, 79.61%; H, 10.95%; N,
1.00%; O, 7.82%. MALDI-TOF MS: molecular weight calcd
(7a -d ) A solution of the appropriate vinyl compound (6a -
d ) (1.2 equiv), Pd(OAc)2 (0.04 equiv), ToP (0.06 equiv), and
4-iodophenol (1 equiv) in dry NEt3 (c ) 0.3 mol/L) was stirred
for 2 h at 60 °C under argon. Then the mixture was stirred
for 1 day at 80 °C. After the reaction was complete, the solvent
was removed under vacuum. The crude product was dissolved
in CH2Cl2 and washed with water and dried over MgSO4, and
the solvent was evaporated. The crude product was purified
by column chromatography on silica gel (eluent petroleum
ether-CH2Cl2: 3-7) followed by an additional recrystallization
in petroleum ether. 7a : 75%, white solid. 1H NMR (CDCl3): δ
7.39 (d, 2H, J ) 8.7 Hz), 6.86 (m, 4H), 6.69 (s, 2H), 4.81 (s,
1H), 3.99 (m, 6H), 1.79 (m, 6H), 1.27 (m, 54H), 0.89 (t, 9H, J
1
) 6.7 Hz). 7b: 60%, white solid. H NMR (CDCl3): δ 7.39 (d,
2H, J ) 8.6 Hz), 6.90 (m, 7H), 4.94 (s, 1H), 4.01 (m, 4H), 1.82
(m, 4H), 1.27 (m, 36H), 0.89 (t, 6H, J ) 6.7 Hz). 7c: 65%, white
1
solid. H NMR (CDCl3): δ 7.39 (d, 2H, J ) 8.7 Hz), 6.87 (m,
for C564H908N6O44: m/z: 8477.3. Found: m/z: 8481.0. 10b:
1
4H), 6.31 (d, 2H, J ) 2.0 Hz), 6.38 (s, 1H), 3.96 (m, 4H), 1.77
25%, white solid. H NMR (CD2Cl2): δ 7.80 (m, 8H), 7.42 (m,

Macromolecules, Vol. 36, No. 15, 2003
Liquid Crystalline Octopus 5601
D. J . P. J . Am. Chem. Soc. 1998, 120, 11061-11070. (d)
Hudson, S. D.; J ung, H. T.; Kewsuwan, P.; Percec, V.; Cho,
W. D. Liq. Cryst. 1999, 26, 1493-1499. (e) Ungar, G.; Percec,
V.; Holerca, M. N.; J ohansson, G.; Heck, J . A. Chem.sEur.
J . 2000, 6, 1258-1266. (f) Percec, V.; Cho, W. D.; Ungar, G.;
Yeardley, D. J . P. Angew. Chem., Int. Ed. 2000, 39, 1597-
1602. (g) Percec, V.; Cho, W. D.; Mo¨ller, M.; Prokhorova, S.
A.; Ungar, G.; Yeardley, D. J . P. J . Am. Chem. Soc. 2000,
122, 4249-4250. (h) Percec, V.; Cho, W. D.; Ungar, G. J . Am.
Chem. Soc. 2000, 122, 10273-10281. (i) Percec, V.; Cho, W.
D.; Ungar, G.; Yeardley, D. J . P. J . Am. Chem. Soc. 2001,
123, 1302-1315. (j) Ungar, G.; Liu, Y.; Zeng, X.; Percec, V.;
Cho, W. D. Science 2003, 299, 1208-1211.
24H), 6.98 (m, 68H), 6.62 (m, 8H), 6.40 (s, 4H), 4.01 (m, 64H),
3.47 (m, 8H), 2.49 (m, 12H), 1.79 (m, 64H), 1.27 (m, 412H),
0.89 (t, 48H, J ) 6,8 Hz). 13C NMR (CDCl3): 160.5, 158.6,
149.3, 148.8, 138.6, 130.9, 130.2, 127.4, 126.4, 126.3, 119.6,
114.6, 113.9, 111.4, 105.3, 69.3, 68.0, 31.9, 29.7, 29.4, 29.3, 29.2,
26.1, 22.7, 14.1. Anal. Calcd for C468H720N6O36: C, 80.22%; H,
10.36%; N, 1.2%. Found: C, 79.46%; H, 10.38%; N, 1.01%.
MALDI-TOF MS: molecular weight calcd for C468H720N6O36
:
m/z: 7005.9. Found: m/z: 7006.68. 10c: 45%, colorless viscous
oil. 1H NMR (CD2Cl2): δ 7.75 (d, 8H, J ) 8.8 Hz), 7.43 (m,
24H), 6.98 (m, 40H), 6.61 (s, 24H), 6.41 (m, 16H), 3.92 (m,
64H), 3.48 (m, 8H), 2.49 (m, 12H), 1.76 (m, 64H), 1.27 (m,
412H), 0.89 (t, 48H, J ) 6.6 Hz). 13C NMR (CDCl3): δ 166.9,
160.3, 159.8, 158.8, 149.5, 143.7, 140.0, 139.4, 138.5, 133.3,
130.5, 129.6, 129.1, 128.3, 127.6, 127.3, 126.3, 114.5, 113.8,
106.9, 105.1, 104.6, 101.2, 100.4, 100.3, 67.9, 54.1, 53.6, 53.0,
52.5, 51.9, 29.4, 22.5, 13.9. Anal. Calcd for C468H720N6O36: C,
80.22%; H, 10.36%; N, 1.2%. Found: C, 80.11%; H, 10.39%;
N, 0.77%. MALDI-TOF MS: molecular weight calcd for
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C
468H720N6O36: m/z: 7005.9. Found: m/z: 7005.3.
Su p p or tin g In for m a tion Ava ila ble: Mass spectra for
10a , 10b, and 10c. This material is available free of charge
via the Internet at http://pubs.acs.org.
Refer en ces a n d Notes
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2
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(22) Molecular volume of the acidic branches, calculated in the
same way as for 10a -c: 8a : 3430 Å3; 8c: 2805 Å3.
MA034038I