Cell membrane as a model for the design of semifluorinated ion-selective nanostructured supramolecular systems

Article abstract of DOI:10.1016/S0040-4020(02)00266-1

The synthesis and polymerization of two AB₃ tapered, self-assembling methacrylate monomers (12 and 13) based on a first generation semifluorinated alkyl-substituted monodendron (i.e. minidendron) are described. These monomers contain either a benzo-15-crown-5 derivative, which is incorporated via the esterification of 4′-hydroxymethyl-1,4,7,10,13-pentaoxabenzocyclopentadecane or a podant group, which is incorporated via the monoesterification of tetraethylene glycol at its focal point, and both bear polymerizable groups on their periphery. The corresponding polymers (14-16) self-assemble and subsequently self-organize into supramolecular networks, which form a 2-D hexagonal columnar lattice via the fluorophobic effect. These networks consist of a continuous phase, which is based on the semifluorinated, paraffinic barrier layer and which is perforated in a hexagonal array by ion-selective or ion-active channels constructed from the benzo crown-ether and tetraethylene glycol respectively. The replacement of alkyl groups from the periphery of the tapered monodendrons with semifluorinated ones induces the self-assembly and, subsequently, the self-organization into supramolecular networks. These networks form 2-D hexagonal columnar lattices with thermal stability in some cases of up to 110°C. The design of such functional supramolecular systems was inspired by the bilayer fluid mosaic structure of the cell membrane. The lipid bilayer of the cell membrane, which in its ordered state acts as a barrier to the passage of polar molecules, was replaced with the semifluorinated paraffinic barrier, while the protein-based ionic channels were replaced with benzo-15-crown-5 and tetraethylene glycol based channels. The resulting supramolecular material has the mechanical integrity required for both ion-active and ion-selective nanostructured supramolecular systems.

Full text of DOI:10.1016/S0040-4020(02)00266-1

TETRAHEDRON
Pergamon
Tetrahedron 58 +2002) 4031±4040
Cell membrane as a model for the design of semi¯uorinated
ion-selective nanostructured supramolecular systems
p
Virgil Percec and Tushar K. Bera
Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, PA 19104-6323, USA
Received 7 November 2001; accepted 14December 2001
3
AbstractÐThe synthesis and polymerization of two AB tapered, self-assembling methacrylate monomers +12 and 13) based on a ®rst
generation semi¯uorinated alkyl-substituted monodendron +i.e. minidendron) are described. These monomers contain either a benzo-15-
0
crown-5 derivative, which is incorporated via the esteri®cation of 4 -hydroxymethyl-1,4,7,10,13-pentaoxabenzocyclopentadecane or a
podant group, which is incorporated via the monoesteri®cation of tetraethylene glycol at its focal point, and both bear polymerizable groups
on their periphery. The corresponding polymers +14±16) self-assemble and subsequently self-organize into supramolecular networks, which
form a 2-D hexagonal columnar lattice via the ¯uorophobic effect. These networks consist of a continuous phase, which is based on the
semi¯uorinated, paraf®nic barrier layer and which is perforated in a hexagonal array by ion-selective or ion-active channels constructed from
the benzo crown-ether and tetraethylene glycol respectively. The replacement of alkyl groups from the periphery of the tapered mono-
dendrons with semi¯uorinated ones induces the self-assembly and, subsequently, the self-organization into supramolecular networks. These
networks form 2-D hexagonal columnar lattices with thermal stability in some cases of up to 1108C. The design of such functional
supramolecular systems was inspired by the bilayer ¯uid mosaic structure of the cell membrane. The lipid bilayer of the cell membrane,
which in its ordered state acts as a barrier to the passage of polar molecules, was replaced with the semi¯uorinated paraf®nic barrier, while the
protein-based ionic channels were replaced with benzo-15-crown-5 and tetraethylene glycol based channels. The resulting supramolecular
material has the mechanical integrity required for both ion-active and ion-selective nanostructured supramolecular systems. q 2002 Elsevier
Science Ltd. All rights reserved.
1. Introduction
transport properties and therefore the cell membrane loses
its fundamental functions.
1
,2
The ¯uid mosaic model of the cell membrane consists of a
self-assembled lipid bilayer containing protein-based active
elements that are co-assembled in the bilayer structure. In its
ordered state, the lipid bilayer is an excellent barrier to polar
molecules and, as a consequence, has the capability to
partition discrete metabolic aqueous compartments. The
impermeability of the lipid bilayer to polar or charged
molecules allows the solute concentration on each of its
sides to differ dramatically. The second function of the
lipid bilayer is to accommodate proteins with various
tertiary structures that are able to provide and control the
transfer of energy and materials and also to act as catalysts.
Simultaneously, the cell membrane has the ability to
respond to changing external conditions that may demand
that certain molecules and ion-pairs pass through the lipid
bilayer +Fig. 1). The proteins that penetrate the bilayer
structure are bound to the membrane mostly by hydrophobic
interactions. In its disordered state, i.e. above the physio-
logical temperature, the lipid bilayer loses its barrier and
A similar synthetic supramolecular system capable of being
externally regulated could have immense technological
implications for areas such as selective membranes, ionic,
protonic and electronic conductors, enzyme-like catalysis,
energy transfer and conversion, particularly if all these
applications could be exhibited by one self-assembled
unit. A synthetic system must not copy the cell membrane
concept, but use its principles as a model to create a system
that is adaptable to the current technological methods.
Therefore, the lipid bilayer barrier may be replaced with
an alternative barrier material that has the required combi-
nation of order and ¯uidity, at least during certain stages of
its self-assembly and self-organization. Simultaneously, the
membrane proteins may be replaced with currently avail-
able ion-selective or ion-active elements such as crown-
ethers or polypodants. The latter should be equipped with
the ability to spontaneously self-assemble into channels,
which are incorporated in the barrier part of the material.
By analogy with a protein-based ionic channel, this material
should be able to ¯ux energy and materials between various
compartments. New synthetic mechanisms to externally
regulate the on and off states of the channel should be
discovered and/or designed. Therefore, bio-inspired design
and synthesis are not necessarily expected to duplicate
Keywords: hexagonal columnar; dendritic monomer; semi¯uorinated alkyl
group; cell membrane; polymerization; nanostructured supramolecular
network.
p
Corresponding author. Tel.: 11-215-573-5527; fax: 11-215-573-7888;
e-mail: percec@sas.upenn.edu
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020+02) 00266-1

4032
V. Percec, T. K. Bera / Tetrahedron 58 ꢀ2002) 4031±4040
Figure 1. Schematic representation of the bilayer ¯uid mosaic model of the cell membrane. Integral proteins are embedded in the bilayer composed of
phospholipids.
concepts from nature and may lead to new concepts suitable
for related or different functions.
would possess many of the characteristics available in the
¯uid mosaic model of the cell membrane +Fig. 1). The
aliphatic tails of the tapered groups +Fig. 2+b)) represent
more than 80% of the entire supramolecular assembly
and, therefore, provide an excellent and inexpensive barrier
material. The functionalization of the tapered building
blocks with a single polymerizable group on their periphery
+Fig. 2+b)) provides, after polymerization, a soluble supra-
molecular network, which has multiple possibilities for the
alignment of its active channels and may be processed in a
variety of ways. In addition, the introduction in the core of
the taper of more than one active element followed by
incorporation into a suitable macromolecular architecture
could yield membranes with multiple channel functionality
useful for ionic, protonic and electronic transport, catalysis
and for other functions. This architectural design contrasts
with the one in which the polymerizable group is attached to
the apex of the monodendron and the resulting polymer
With the goal of creating ion-selective and ion-active self-
regulated supramolecular systems we have pioneered the
design and synthesis of conventional side-chain, main-
2
3
4
chain and macrocyclic liquid crystalline polymers and
oligomers containing crown-ethers and polypodants as
ion-active elements. In all cases, calamitic mesogenic
groups have been employed to induce 1-D or 2-D liquid-
like nematic and smectic order which is complemented by
ionic activity. Polymerization has been used as the most
frequent tool to enable mechanical integrity and provide a
5
,6
broad range of thermal stability in the liquid ordered state.
A second and more ef®cient class of building blocks that
self-assemble into ionic channels, and which subsequently
self-organize in a 2-D hexagonal columnar lattice, has been
studied in our laboratory. In this case the concept is based on
tapered minidendritic units containing crown-ethers or oligo
1
0c±i
exhibits a cylindrical structure +Fig. 2+a)),
rather than
a network of cylinders. Last but not least, self-organized
supramolecular structure of the synthetic nanostructured
material described in Fig. 2+b) may provide access to
features such as self-repair and external regulation.
+
development of both molecular and macromolecular
ethylene oxide) units at their core +Fig. 2), leading to the
6
7
ion-active systems. Enhanced conductivity along these
ion-channels which are organized in a hexagonal columnar
6
a,c
2
together with structural studies
-D lattice was reported from our laboratory,
and
has demonstrated the
One of the major requirements for such a nanostructured
supramolecular system is that the 2-D self-organized struc-
ture should persist over a broad temperature range, thus
providing suf®cient thermal stability. Previously designed
ion-selective and ion-active systems only self-assemble in a
6
a,b,e,f
structure of these assemblies. Subsequently, increased ionic
conductivity in other liquid crystalline states was reported
from other laboratories.
8
2-D hexagonal columnar ¯uid lattice after complexation
with metal salts.
1
0±12
Self-assembling tapered molecules containing crown-ethers
were recently employed in a new concept for the design of
functional nanoporous membranes known as gel template
Recently, we reported the design and
synthesis of AB tapered minidendritic benzyl ethers, which
3
contain oligooxyethylene units with different chain length
as ion-active elements in their core and a single polymeriz-
able group on their periphery. The polymers obtained from
9
10a,b
11
leaching. The mono
and multifunctionalization of the
1
3
periphery of these building blocks with polymerizable
groups has been used in the design of self-organized soluble
and insoluble nanostructured membranes. We believe that
the self-assembling tapered groups containing active
element+s) in their core and one or more polymerizable
groups on their periphery can be developed for use in the
generation of multifunctional membranes. Such membranes
these AB tapered minidendritic monomers form supra-
3
molecular networks with narrow thermal stability of their
2-D hexagonal columnar +f ) liquid crystalline phase. The
h
2-D hexagonal columnar lattice is responsible both for the
barrier and transport properties of these new materials,
therefore, an extension of its thermal stability is desirable.

V. Percec, T. K. Bera / Tetrahedron 58 ꢀ2002) 4031±4040
4033
Figure 2. Self-assembly and self-organization followed by polymerization or polymerization followed by self-assembly and self-organization of tapered
monodendrons containing a polymerizable group at the apex +a) or on the periphery of the taper +b). The R group in +b) represents the ionic, electronic or
protonic active element.
An approach towards this goal would be to design higher
2. Results and discussion
1
4
generation tapered dendritic monomers, which have the
potential to broaden the thermal stability of the resulting
functional polymers. However, this requires extensive
molecular design and synthetic effort and faces the perma-
2.1. Synthesis of tapered semi¯uorinated monomers and
polymers
1
4
nent challenge of self-assembly in a 3-D cubic lattice
The monomethacrylate-functionalized monodendrons such
as 1,4,7,10,13-pentaoxabenzocyclopentadecane-2-ylmethyl-
3-+11-methacryloylundecyloxy)-4,5-bis +12,12,12,11,11,10,
10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uoro dodecan-1-yloxy)
benzoate +12) and 2-{2-[2-+2-tert-butyl dimethyl siloxy
rather than a 2-D hexagonal columnar lattice. A second
approach would be to replace the alkyl groups on the
periphery of the tapered dendrons with semi¯uorinated
ones. Previously, we have demonstrated that the ¯uoro-
phobic effect induces self-assembly of semi¯uorinated
ethoxy) ethoxy] ethoxy} ethyl-3-+11-methacryloylundecyl-
oxy)-4,5-bis
6e,7e,f
monodendrons into supramolecular columnar dendrimers,
while their parent hydrogenated monodendrons do not self-
assemble. Subsequently, it has been demonstrated that this
+12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-
heptadeca¯uoro dodecan-1-yloxy) benzoate +13) were
synthesized as outlined in Schemes 1 and 2. The synthetic
strategy used here starts with the protection of two phenolic
OH groups of 3,4,5 trihydroxy methyl benzoate +1). This
was accomplished by reacting 1 with acetone in presence of
the dehydrating agent P O to obtain 3,4-isopropyliden-5-
1
1
5
6
effect plays a role in the ®eld of rod-like liquid crystals
and, more recently, also in other self-assembled systems,
including the ®eld of peptides.
1
7
2
5
2
3
In this publication, we report the design and synthesis of
semi¯uorinated AB methacrylate monomers containing a
hydroxy methyl benzoate +2) in 40% yield after 1 h at
228C. The hydroxy group of 2 was alkylated with
1-bromoundecanol in DMF at 608C, using K CO as base,
3
polymerizable group on their periphery and a benzo-15-
crown-5 group or a podant tetraethylene glycol at their
core. After polymerization, supramolecular networks,
which demonstrate suitable thermal stability for their 2-D
hexagonal columnar liquid crystalline lattice, were achieved
solely via the ¯uorophobic effect and without any additional
ion-mediated interaction process.
2
3
yielding 3 in 85% yield. The deprotection of the isopropyl-
idene-protected group was accomplished in re¯uxing
MeOH/HCl to produce 4 in 94% yield. The next step in
the sequence of reactions involved the etheri®cation of the
two phenolic hydroxy groups of methyl 3,4-dihydroxy-5-
2
3
+11-hydroxyundecyloxy) benzoate +4)
with 12,12,

4034
V. Percec, T. K. Bera / Tetrahedron 58 ꢀ2002) 4031±4040
Scheme 1.
1
dodecyl bromide +5), using anhydrous K CO in DMF
2,11,11,10,10,9,9,8,8,7,7,6,6,5,5,
hepta
deca¯uoro
by basic work up +2N NaOH aqeous solution). In the last
step, the acid was treated with either 4 -hydroxymethyl-
7
f
0
[1,4,7,10,13-pentaoxabenzo cyclopenta decane] +10) or
2
3
6
a
at 708C and yielding methyl 3-+11-hydroxyundecyloxy)-
,5-bis +12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptade-
4
with 2-{2-+2-+2-+2-+tert-butyldimethylsiloxy)
ethoxy) ethoxy) ethanol +11)
ethoxy)
under neutral reaction
1
0f
ca¯uoro dodecan-1-yloxy) benzoate +6) in 89% yield
after recrystallization from acetone +Scheme 1). After
saponi®cation of the ester group of 6 with aqueous KOH in
90% EtOH at re¯ux, the corresponding acid 7 was obtained
in 88% yield. Esteri®cation of this hydroxy-functionalized
conditions +DCC/DPTS) to produce the methacrylate-func-
tionalized monomers 1,4,7,10,13-pentaoxabenzocyclo-
pentadecane-2-ylmethyl-3-+11-methacryloylundecyloxy)-
4,5-bis
+12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-hepta-
acid 7 with methacrylic acid chloride using Et N in CH Cl
2
deca¯uoro dodecan-1-yloxy) benzoate +12) and 2-{2-[2-
+2-tert-butyl dimethyl siloxy ethoxy) ethoxy] ethoxy}
ethyl-3-+11-methacryloylundecyloxy)-4,5-bis +12,12,12,11,
3
2
at 0±58C yielded 3-+11-methacryloylundecyloxy)-4,5-bis
12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uoro
+
dodecan-1-yloxy) benzoic acid +9) in 89% yield after the
mixed benzoic methacryloyl anhydride +8) was hydrolyzed
11,10,10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uoro dodecan-1-
yloxy) benzoate +13) in 79 and 73% yields, respectively,

V. Percec, T. K. Bera / Tetrahedron 58 ꢀ2002) 4031±4040
4035
Scheme 2.
after puri®cation by column chromatography +SiO , 10%
2
EtOAc in hexanes) +Scheme 2).
yields after puri®cation by column chromatography
+Al O , CH Cl as eluent to remove unreacted monomer)
2
3
2
2
+Scheme 3). The removal of the TBDMS group of 15 was
Polymerization of the resulting methacrylates 12 and 13 was
performed at 808C in a,a,a-tri¯uoro toluene +50 wt%) using
1.0 wt% AIBN as radical initiator +Scheme 3). The resulting
polymethacrylates 14 and 15 were obtained in 60±65%
conveniently performed using HF/Py in THF at 228C to
produce polymethacylate 16 in 95% yield. Polymethacrylate
16 is insoluble in common organic solvents but soluble in
¯uorinated ones, i.e. a,a,a-tri¯uoro toluene. The molecular
Scheme 3.

4036
V. Percec, T. K. Bera / Tetrahedron 58 ꢀ2002) 4031±4040
Table 1. Structural and thermal analysis of the polymers 14±16
Polymer
Yield +%)
Mn +GPC)
Mw/Mn +GPC)
Thermal transitions +8C) and corresponding enthalpy changes
a
+
Kcal/mol)
Heating
Cooling
14
15
16
65
60
±
20,000
33,491
±
1.30
1.47
±
g 30.0 k 55.7 +3.21) F
h
99.0 +0.31) i
i 90.5 +20.24) F
g
h
h
25.5
9.0
g 29.0 F
g 21.0 F
g 2.0 F 36.4+0.29) i
g 20.0 F 111.0 +0.67) i
k 19.0 +2.31) F 106.0 +0.60) i
h
100.5 +0.22) i
h
38.0 +0.37) i
i 23.1 +0.32) F
20.9 g
h
h
h
i 95.3 +20.62) F
+22.35) k
h
a
Data on the ®rst line under heating were obtained during the ®rst heating scan. Data on the second line under heating were obtained during second heating
scan.
Ê
column diameter by 3 A when compared with the column
weights of polymethacrylates 14 and 15 relative to
polystyrene standards +Mn) and their molecular weight
distributions +Mw/Mn) are listed in Table 1.
6
a,b,e,f
diameter of 16. More detailed structural analysis
and
6
a,c
conductivity measurements reported previously from our
laboratory have demonstrated that these supramolecular
cylinders contain an ionic channel penetrating through
their center.
2.2. Thermal and structural analysis of polymeth-
acrylates 14±16
The thermal behavior and the structural analysis of poly-
methacrylates 14±16 were carried out by a combination of
techniques that include differential scanning calorimetry
It should be noted that the replacement of the alkyl groups
on the periphery of the tapered dendrons with semi¯uori-
nated ones induces the self-assembly and the self-organiza-
tion into supramolecular columnar networks, thereby
forming a 2-D hexagonal columnar lattice with a broad
+
polarized microscopy +TOPM) experiments according to
DSC), X-ray diffraction +XRD) and thermal optical
2
±4,6,7
standard procedures used in our laboratory.
temperatures and the corresponding enthalpy changes are
Transition
range of thermal stability. The f phase of 15 is stable
h
until 388C, while that of 16 persists until 1118C +Table 1).
Therefore, this approach of replacing two alkyl chains with
two semi¯uorinated ones alleviates the need for the exten-
sive synthetic effort involved in the preparation of higher
generations of tapered dendritic monomers which might
similarly increase the thermal stability. The experiments
described herein expand the synthetic applications of semi-
¯uorinated compounds at the interface between supra-
summarized in Table 1. Monomer 12 displays a monotropic
hexagonal columnar +f ) liquid crystalline phase +see
h
Section 4). However, the corresponding polymer +14)
displays an enantiotropic liquid crystalline phase +Table 1).
This transformation of 12 to 14 also enhances the thermal
stability of the f phase by up to 1008C, polymerization has
h
been used often as a tool to increase the thermal stability of
liquid crystalline states. Polymers 15 and 16 also display
5
,6
2c,24
6
e,f,7e,f,15
molecular
and macromolecular
chemistry.
an enantiotropic hexagonal columnar +f ) liquid crystalline
h
+
LC) phase, despite the fact that their monomeric precusor is
liquid. The assignment of the mesophase was made by small
and wide angle XRD experiments. The d-spacings of all
re¯ections are presented in Table 2 together with their
lattice parameter +a). Bragg diffraction peaks corresponding
3. Conclusions
The synthesis and polymerization of two AB3 self-
assembling methacrylate monomers 12 and 13 based on
the ®rst generation semi¯uorinated alkyl substituted mono-
dendrons +i.e. minidendrons) containing a benzo-15-crown-
5 derivative, which is incorporated via the esteri®cation of
p
p
to a lattice spacing in a ratio of 1:1/ 3:1/ 7, which are
1
8±22
characteristic of a 2-D hexagonal columnar lattice,
exhibited at small angles by 14±16. The thermal stability of
are
0
the f phase of 16 increased by 708C from that of 15 by
h
4 -hydroxymethyl-1,4,7,10,13-pentaoxabenzocyclopenta-
removing the tert-butyl dimethyl silyl group from the core
of 15. This enhanced thermal stability of 16 is due to the
H-bonding interactions of the tetraethylene glycol present in
the core of the supramolecular column. However, the
presence of tert-butyl dimethyl silyl group in the core of
the supramolecular column of 15 contributed to an increased
decane or a podant which is incorporated via the mono-
esteri®cation of tetraethylene glycol at its focal point and
a polymerizable group on their periphery are described. The
corresponding polymers 14±16 self-assemble and self-
organize into supramolecular networks that form a 2-D
hexagonal columnar lattice solely via the ¯uorophobic
6
a,b,e,f
effect. By analogy with related structures,
consists of a continuous phase, which is based on a semi-
uorinated, paraf®nic barrier layers and which is perforated
this network
Table 2. Structural analysis by X-ray diffraction of polymers 14±16
¯
a
b
a
Ê
Ê
Ê
in a hexagonal array by ion-active channels constructed
from the benzo-15-crown-5 and tetraethylene glycol,
respectively. All polymers display an enantiotropic
hexagonal columnar liquid crystalline phase. These poly-
mers exhibit a range of thermal stability of their hexagonal
columnar phase of up to 1108C. These experiments have
demonstrated that the replacement of alkyl chains with
Polymer Temp. +8C)
d
100 +A)
d
110 +A)
d
210 +A) kd100
l
13
14
15
90
32
85
41.5
43.2
40.3
22.1
22.7
20.9
14.7
15.4
14.3
39.6
41.0
38.0
45.7
47.3
43.9
p
Lattice dimension.
p
p
a
kd100lˆ+d1001 3d1101 7d210)/3; aˆ2kd100l/ 3.
b

V. Percec, T. K. Bera / Tetrahedron 58 ꢀ2002) 4031±4040
4037
semi¯uorinated ones alleviates the need for extensive
synthetic effort when synthesizing higher generation
dendritic monomers, which would have the potential to
broaden the thermal stability of the 2-D hexagonal lattice
of the resulting functional polymers. The enhancement of
tial scanning calorimeter. In all cases the heating and
cooling rates were 108C/min. First order transitions were
reported as the maxima or minima of the endothermic and
exothermic peaks during the second heating and cooling
scans. Glass transition temperatures +T ) were measured as
g
the thermal stability of the f phase of 16 by up to 708C is
h
achieved by removal of the TBDMS protection group from
the core of 15.
the middle point of the change in heat capacity. Zn and In
were used as calibration standards. X-Ray diffraction
experiments were performed using a multi-wire area detec-
tor +Siemens) with a Cu Ka1 radiation obtained from a rotat-
ing anode +Nonius FR591) X-ray generator after passing
through a set of mirrors and then a monochromator. The
X-ray beam path is under low vacuum to reduce the back-
ground scattering from air. Powdered samples were held at
constant temperature +^0.18C) in a temperature-controlled
cell. An Olympus BX-40 optical polarized microscope
+100£ magni®cation) equipped with a Mettler FP 82 hot
stage and a Metler FP 80 central processor was used to
verify thermal transitions and to characterize the anisotropic
textures. The elemental analysis +C, H) of all new
compounds were performed by M-H-W Laboratories,
Phoenix, A.
4. Experimental
4
.1. General
4
-Dimethylamino pyridine +DMAP, 98%, Fluka), 1,3-
dicyclohexyl carbodiimide +DCC, 99%, Aldrich), HCl
A.C.S. Reagents, Fisher Scienti®c), MgSO4 +Fisher
Scienti®c), LiAlH +95%, Aldrich), a,a,a-tri¯uoro toluene
+
4
+
+
Aldrich, 991%), 1,1,2-trichlorotri¯uoroethane +Freon)
Aldrich, 99.8%) were used as received. THF +A.C.S.
Reagents, Fisher Scienti®c) was dried over sodium/benzo-
phenone ketyl and distilled before use. NEt +99%, Aldrich)
3
was dried over CaH and distilled before use. DMF +A.C.S.
2
4.1.1. Methyl-3-ꢀ11-hydroxyundecyloxy)-4,5-bis ꢀ12,12,
12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uorodode-
can-1-yloxy) bezoate ꢀ6). To a round bottom ¯ask equipped
with a nitrogen inlet±outlet, containing a degased stirring
Reagents, Fisher Scienti®c) was dried over CaH2 and
distilled under vacuum. CH Cl +A.C.S. Reagents, Fisher
Scienti®c) was dried over CaH and distilled. Benzene
2
2
2
+
of H SO until they remained relatively uncolored, washed
A.C.S., Fisher Scienti®c) was washed with 50 mL portions
mixture of 4 +1.5 g, 4.23 mmol) and K
2
CO
3
+5 g,
36.17 mmol) in 60 mL of DMF at 608C, was added 5
+5.17 g, 9.31 mmol) in small portions over 10 min. After
24h at 60 8C, the reaction mixture was poured into a
500 mL of ice-water. The resulting solid was ®ltered and
washed with water twice. After recrystallization from ace-
tone, 4.9 g +89%) of white solid 6 was obtained. Purity: 99%
2
4
with H O to neutral pH, dried over MgSO , ®ltered, dried
2
4
over sodium/benzophenone ketyl and distilled before use.
Azobisisobutyronitrile +AIBN, Fluka) was recrystallized
from methanol below 408C. Tetraethylene glycol +99%,
Aldrich) was dried over sodium and distilled under vacuum
before use. 4-Dimethylaminopyridinium-p-toluene sulfo-
+HPLC). Mp 57±588C TLC: R
ˆ0.28 +2:1 hexanes/EtOAc).
H NMR +200 MHz, CDCl , 208C): d 1.1±1.2 +overlapped
3
f
6
a
1
nate +DPTS),
hepta deca¯uoro dodecyl bromide +5), methyl-3-+11-
12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5,
7
f
peaks, 26H), 2.2±2.3 +m, 4H), 3.4 +t, 2H, Jˆ6.6 Hz), 3.9 +s,
3H), 4.1 +m, 6H), 7.3 +s, 2H). C NMR +50 MHz, CDCl ,
3
2
hydroxy undecyloxy)-4,5-dihydroxy benzoate +4), 4 -
3
0
13
hydroxymethyl-[1,4,7,10,13-pentaoxabenzo
cyclopenta
2-{2-+2-+2-+2-+tert-butyldimethylsiloxy)
208C): d 17.2, 25.7±32.8 +m), 52.1, 62.9, 68.4, 69.1, 72.5,
107.8, 108.1, 125.1, 141.9, 152.5, 152.9, 166.8. Elemental
6
a
decane] +10),
ethoxy) ethoxy) ethoxy) ethanol +11), were synthesized
1
0f
analysis: calcd for C43
C, 39.57; H, 3.45.
H O F34: C, 39.61; H, 3.47. Found.
45 6
1
according to literature procedures. H NMR, +200 MHz),
1
3
19
C NMR +50 MHz) and F NMR +188 MHz) spectra
were recorded on a Varian Gemini 200 spectrometer with
tetramethylsilane +TMS) internal standard for H NMR and
4.1.2. 3-ꢀ11-Hydroxyundecyloxy)-4,5-bis ꢀ12,12,12,11,
11,10,10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uorododecan-1-
yloxy) benzoic acid ꢀ7). In a 250 mL round-bottom ¯ask
containing a Te¯on coated magnetic stir bar was placed
4.8 g +3.68 mmol) of 6, 40 mL of 90% EtOH, and 0.7 g
+12.47 mmol) of KOH pellets. The mixture was re¯uxed
1
1
3
C and ¯uorotrichloromethane +CFCl ) internal standard
3
1
9
for F. Chromatographic puri®cation was conducted using
00±400 mesh silica gel obtained from Natland Inter-
2
national Corporation, Morrisville, NC. Relative molecular
weights were determined using a Perkin±Elmer Series 10
GPC equipped with a LC-100 column oven +408C), Nelson
Analytical 900 Series integrator data station, and two
under N for 2 h. The reaction mixture was cooled to 228C
2
and the resulting solids were dissolved in 100 mL of hot
THF with stirring. The solution was cooled to 08C and acidi-
®ed with conc. HCl. The solution was poured into 500 mL
2
Polymer Laboratories PL gel columns of 5£10 and
4
0 A, and THF as eluent at 1 mL/min. Detection was by
Ê
1
of ice-water and extracted with Et O +3£100 mL). The
2
UV absorbance at 254nm. Relative weight average +Mw)
and number average +Mn) molecular weights were calcu-
lated by using a calibration plot constructed from poly-
styrene standards. High pressure liquid chromatography
combined Et O extract was washed with water
2
+2£200 mL), brine +2£200 mL) and dried over MgSO
.
4
The solution was ®ltered and the solvent was evaporated,
resulting in 4.2 g +88%) of white crystals 7. Mp 94±968C.
1
+
HPLC) experiments were performed with the same instru-
Purity: 99% +HPLC). TLC: R
NMR +200 MHz, CDCl
26H), 2.2±2.3 +m, 4H), 3.4 +t, 2H, Jˆ6.7 Hz), 4.1 +m, 6H),
f
ˆ0 +2:1 hexanes/EtOAc). H
ment. Gas chromatography analysis +GC) was performed on
a Hewlett±Packard 5890 gas chromatograph equipped with
a packed column of 10% SP 2100 on 80/100 Supelcoport
and a Hewlett±Packard 3392A integrator. Thermal transi-
tions were determined on a Perkin±Elmer DSC-7 differen-
, 208C): d 1.1±1.2 +overlapped m,
3
1
9
7.3 +s, 2H). F NMR +188 MHz, CD
208C): d 279.9 +s, 6F, CF ), 2113.1 +s, 4F, CH
2120.7 +s, 12F +CF ), 2121.6 +s, 4F, CF CF CH
2
COCD
, CFCl
,
3
3
3
CF
2
),
),
3
2
)
2
3
2
2

4038
V. Percec, T. K. Bera / Tetrahedron 58 ꢀ2002) 4031±4040
1
3
2
NMR +50 MHz, CDCl , 208C): d 18.1, 26.8±34, 62.5, 69.2,
122.2 +s, 4F, CF CF CF ), 2125.1 +s, 4F, CF CF ).
C
Elemental analysis: calcd for C H O F : C, 44.72; H,
61 67 12 34
3
2
2
3
2
4.11. Found. C, 44.20; H, 4.30. DSC: 1st heating: k 45.71
k 67.11 i. 2nd heating: k 33.3 k 61.20 i. 1st cooling i 42.45
F +25.72) 24.84 k.
3
69.8, 73.2, 108.8, 109.1, 126.5, 141.3, 153.7, 152.9, 166.8.
Elemental analysis: calcd for C H O F : C, 39.11; H,
4
2
43
6
34
h
3
.35. Found. C, 38.87; H, 3.29.
4.1.5. 2-{2-[2-ꢀ2-tert-Butyl dimethyl siloxy ethoxy)
4
1
1
.1.3. 3-ꢀ11-Methacryloylundecyloxy)-4,5-bis ꢀ12,12,12,
1,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uorododecan-
-yloxy) benzoic acid ꢀ9). 1.6 g +15.3 mmol) freshly
ethoxy] ethoxy} ethyl-3-ꢀ11-methacryloylundecyloxy)-
4,5-bis ꢀ12,12,12,11,11,10,10,9,9, 8,8,7,7,6,6,5,5-heptade-
ca¯uorododecan-1-yloxy) benzoate ꢀ13). To a well stirred
solution of 9 +2.0 g, 1.47 mmol) and 11 +0.63 g, 2.04mmol)
distilled methacryloyl chloride was slowly added to a cold
08C) solution of 7 +4.0 g, 3.1 mmol) and Et N +1.54g,
+
in 25 mL dry CH
trichlorotri¯uoroethane, DCC +0.9 g, 4.36 mmol) was
added under N . DPTS +0.04g, 0.13 mmol) was added
2
Cl
2
and 15 mL dry 1,1,2-
3
1
5.3 mmol) in 40 mL CH Cl under N . The ice cooling
2 2 2
was removed, and the reaction mixture was stirred at 228C
for 24h. The reaction mixture was concentrated and diluted
with 200 mL of Et O and washed with H O +2£100 mL), 2N
2
last. The reaction mixture was stirred at 228C for 24h.
The reaction mixture was diluted with 100 mL of hexanes
and ®ltered. The raw product +viscous mass) was puri®ed by
2
2
NaOH +3£100 mL), 2N HCl +2£100 mL), H O
2
+
organic phase was dried over MgSO , and the solvent was
2£100 mL), and ®nally with brine +1£200 mL). The
column chromatography +SiO
yield 1.76 g +73%) of 13 as a colorless viscous liquid.
Purity: 99% +HPLC). TLC: R
ˆ0.44 +2:1 hexanes/EtOAc).
, 208C): d 0.05 +s, 6H), 0.88 +s,
, 10% EtOAc in hexanes) to
2
4
removed in vacuo. After recrystallization from acetone,
3
f
1
.74g +89%) of white solid 9 was obtained. Purity: 98%
H NMR +200 MHz, CDCl
3
1
+
+
HPLC). TLC: R ˆ0 +2:1 hexanes/EtOAc). H NMR
9H), 1.29±2.04+m, 29H, 2.17±2.3 +m, 4H ), 3.54+t, 2H
f
200 MHz, CDCl , 208C): d 1.18±1.95 +overlapped m,
3
Jˆ6.5 Hz), 3.64±3.83 +m, 12H), 4.02±4.16 +m, 8H), 4.46
2
1
9H), 2.05±2.27 +m, 4H), 4.01±4.23 +m, 8H), 5.55 +s,
H), 6.1 +s, 1H), 7.33±7.35 +d, 2H, Jˆ4Hz). F NMR
+t, 2H, Jˆ6.7 Hz), 5.53 +s, 1H), 6.09 +s, 1H), 7.27±7.29 +d,
COCD , CFCl
3 3 3
1
9
19
2H, Jˆ3.95 Hz). F NMR +188 MHz, CD
+188 MHz, CD COCD , CFCl 208C): d 281.9 +s, 6F,
CF ), 2115.2 +s, 4F, CH CF ), 2122.7 +s, 12F, +CF ) ),
208C): d 280.1 +s, 6F, CF
2120.9 +s, 12F, +CF ), 2121.6 +s, 4F, CF
2125.2 +s, 4F, CF CF CF ), 2128.4+s, 4F , CF
NMR +50 MHz, CDCl
3
), 2114.0 +s, 4F, CH
2
CF
CH
).
2
),
),
C
3
3
3
)
3
CF
CF
3
2
2
2 3
2
2
2
2
3
1
2
2
123.5 +s, 4F, CF CF CH ), 2124.2 +s, 4F, CF CF CF ),
2
3
2
2
3
2
2
2
2
3
2
1
127.1 +s, 4F, CF CF ). C NMR +50 MHz, CDCl , 208C):
3
, 208C): d 25.09, 17.6, 18.4, 26.3,
3
3
2
3
d 18.1, 26.8±34.0 +m), 62.5, 69.2, 69.8, 73.2, 108.8, 109.1,
26.5, 141.3, 153.7, 152.9, 166.8. Elemental analysis: calcd
for C H O F : C, 40.69; H, 3.48. Found. C, 40.10; H,
28.8±31.4 +m), 63.01, 64.4, 65.0, 68.8, 69.5, 72.7, 108.3,
108.7, 125.1, 125.4, 137.2, 152.7±153.1 +m), 166.2.
1
Elemental analysis: calcd for C60
4.70. Found. C, 43.96; H, 4.57.
H O11SiF34: C, 43.75; H,
77
4
6
47
7 34
3
.52.
4
.1.4.
1,4,7,10,13-Pentaoxabenzocyclopentadecane-2-
4.2. Polymerization of monomers 12 and 13
ylmethyl-3-ꢀ11-methacryloylundecyloxy)-4,5-bis ꢀ12,12,
2,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uorodode-
can-1-yloxy) benzoate ꢀ12). To a well stirred solution of 9
1.16 g, 0.85 mmol) and 10 +0.29 g, 0.97 mmol) in 20 mL
dry CH Cl and 10 mL 1,1,2-trichlorotri¯uoroethane, DCC
1
Both monomers were polymerized as a 50% +w/v) solutions
in a,a,a-tri¯uorotoluene under argon at 808C for 48 h.
AIBN +1% w/w) was used as radical initiator. The polymer-
ization solution was degased by three freeze-pump-thaw
cycles before polymerization. All polymers were separated
from unreacted monomers by column chromatography
+
2
2
+
0.61 g, 3.0 mmol) was added under N . DPTS +0.117 g,
2
0
.4mmol) was added last. The reaction mixture was stirred
at 228C for 24h. The reaction mixture was diluted with
hexanes +50 mL) and ®ltered. The solution was concen-
trated and precipitated in a large excess of methanol three
times. The crude product was puri®ed by column chromato-
+
neutral alumina, CH Cl ). The yield and molecular weight
2 2
distributions and DSC of the polymers obtained are shown
in Table 1.
graphy +SiO , 10% EtOAc in hexanes) to yield 1.1 g +79%)
2
4.2.1. Poly ꢀ1,4,7,10,13-pentaoxabenzocyclopentadecane-
2-ylmethyl-3-ꢀ11-methacryloylundecyloxy)-4,5-bis ꢀ12,
12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uoro
of white solid 12. Purity: 99% +HPLC). TLC: R ˆ0.46 +2:1
f
1
hexanes/EtOAC). H NMR +200 MHz, CDCl , 208C): d
3
1
1
.1±1.95 +overlapped m, 29H), 2.05±2.27 +m, 4H), 3.73
m, 8H, OCH CH O, on benzo crown ether), 3.9 +m, 4H,
dodecan-1-yloxy) benzoate) ꢀ14). H NMR +200 MHz,
CDCl , 208C): d 1.1±2.0 +br, 29H), 2.05±2.3 +br, 4H),
+
ArOCH CH , on benzo crown ether), 4.08 +m, 4H,
2
2
3
2
2
3.73 +br, 8H, OCH CH O, on benzo crown ether), 3.9 +br,
2
2
ArOCH CH , on benzo crown ether), 4.01±4.23 +m, 8H,
2
4H, ArOCH CH , on benzo crown ether), 4.08 +br, 4H,
2 2
2
CH vC+CH )CO CH , CH OAr), 5.18 +s, 2H, CO CH ,
2
ArOCH CH , on benzo crown ether), 4.01±4.3 +m, 8H,
2 2
2
3
2
2
2
2
on benzo crown ether), 5.47 +s, 1H), 6.03 +s, 1H), 6.8±6.9
overlapped peaks, 3H, aromatic protons of benzo crown
ether), 7.1±7.35 +m, 2H, ArH ortho to CO CH ). F NMR
CH vC+CH )CO CH , CH OAr), 5.2 +bs, 2H, CO CH ,
2 3 2 2 2 2 2
+
on benzo crown ether), 6.8±67.0 +br, 3H, aromatic protons
of benzo crown ether), 7.1±7.4+br, 2H, ArH ortho to
CO CH ).
1
9
2
2
+
188 MHz, CD COCD , CFCl 208C): d 280.9 +s, 6F, CF ),
3 3 3 3
2
2
2
114.2 +s, 4F, CH CF ), 2121.7 +s, 12F, +CF ) ), 2121.2
2 2 2 3
+
s, 4F, CF CF CH ), 2125.2 +s, 4F, CF CF CF ), 2128.1 +s,
2
4.2.2. Poly ꢀ2-{2-[2-ꢀ2-tert-butyl dimethyl siloxy ethoxy)
ethoxy] ethoxy} ethyl-3-ꢀ11-methacryloylundecyloxy)-
2
2
3
2
2
1
3
F, CF CF ). C NMR +50 MHz, CDCl , 208C): d 17.5,
4
1
7
1
3
2
3
8.2, 24.1, 26.1±31.05 +m), 64.7, 66.8, 68.4, 69.1, 69.5,
2.4, 107.8, 108., 113.7±114.6 +m), 121.8, 124.9 125.0,
29.0, 140.8, 149.1, 152.4±152.8 +m), 166.15, 168.44.
4,5-bis
deca¯uorododecan-1-yloxy) benzoate) ꢀ15). H NMR
ꢀ12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-hepta-
1
+200 MHz, CDCl , 208C): d 0.05 +bs, 6H), 0.88 +bs, 9H),
3

V. Percec, T. K. Bera / Tetrahedron 58 ꢀ2002) 4031±4040
4039
1
+
2
.3±2.04+br, 29H), 2.2±2.4+br, 4H), 3.54+br, 2H), 3.6±3.8
br, 12H), 4.1±4.2 +br, 8H), 4.4 +br, 2H), 7.2±7.3 +br,
H).
Slanger, P. J. Macromolecules 1995, 28, 8807. +f) Johansson,
G.; Percec, V.; Ungar, G.; Zhou, J. P. Macromolecules 1996,
29, 646. +g) Percec, V.; Schlueter, D.; Ungar, G.; Cheng,
S. Z. D.; Zhang, A. Macromolecules 1998, 31, 1745.
8. +a) McHattie, G. S.; Imrie, C. T.; Ingram, M. D. Electrochim.
Acta 1998, 43, 1151. +b) Zheng, Y.; Chia, F.; Ungar, G.;
Richardson, T. H.; Wright, P. V. Electrochim. Acta 2001,
46, 1397 and references cited therein.
4
.2.3. Poly ꢀ2-{2-[2-ꢀ2-hydroxyethoxy) ethoxy] ethoxy}
ethyl-3-ꢀ11-methacryloylundecyloxy)-4,5 bis ꢀ12,12,
2,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadeca¯uorodode-
can-1-yloxy) benzoate) ꢀ16). Elemental analysis calcd
for C H O F : C, 42.28; H, 4.13. Found. C, 41.23; H,
1
5
4
63 11 34
9. Gankema, H.; Hampenius, M. A.; Moller, M.; Johansson, G.;
È
3
.97.
Percec, V. Macromol. Symp. 1996, 102, 381.
1
0. +a) Percec, V.; Zipp, G.; Johansson, G.; Beginn, U.; M oÈ ller, M.
Macromol. Chem. Phys. 1997, 198, 265. +b) Beginn, U.; Zipp,
G.; M oÈ ller, M.; Johansson, G.; Percec, V. Macromol. Chem.
Phys. 1997, 198, 2839. +c) Percec, V.; Heck, J. J. Polym. Sci.,
Part A: Polym. Chem. 1991, 29, 591. +d) Percec, V.; Schlueter,
D.; Kwon, Y. K.; Blackwell, J.; M oÈ ller, M.; Slangen, J. P.
Macromolecules 1995, 28, 8807. +e) Percec, V.; Schlueter,
D. Macromolecules 1997, 30, 5783. +f) Percec, V.; Schlueter,
D.; Ungar, G.; Cheng, S. Z. D.; Zhang, A. Macromolecules
Acknowledgements
Financial support by Of®ce of Naval Research and National
Science Foundation is gratefully acknowledged.
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