A new family of polymerizable lyotropic liquid crystals: Control of feature size in cross-linked inverted hexagonal assemblies via monomer structure

Article abstract of DOI:10.1021/ja002462i

An efficient and versatile synthesis of a series of polymerizable amphiphilic mesogens that affords control over tail length and position of the polymerizable group is described. The synthesis employs a novel and facile method of preparing styrene ethers. The monomers are sodium salts of styrene ether-modified fatty acids that can be used to form cross-linkable inverted hexagonal (H_II) lyotropic liquid crystal (LLC) phases at ambient temperature with controllable nanometer-scale dimensions. Examination of a series of regioisomers with the same alkyl chain length but with the styrene ether group at different locations along the chain revealed that the position of the styrene ether has a profound effect on the dimensions of the resulting H_II phase at a fixed temperature and composition. Increasing overall monomer tail length also has a significant, although smaller, effect on the unit cell dimensions of the LLC phase. By controlling the structure of the LLC monomer in this manner, cross-linked H_II phases with interchannel distances (ICD) ranging from 29 to 54 A can be obtained. Furthermore, changing the counterion from Na⁺ to tetraalkylammonium ions leads to further expansion of the H_II unit cell to a maximum ICD of 65 A, as well as to the production of a lamellar phase. Use of these monomers affords a new and unparalleled degree of control over phase structure and dimensions for the production of nanostructured organic materials.

Full text of DOI:10.1021/ja002462i

VOLUME 123, NUMBER 3
J ANUARY 24, 2001
© Copyright 2001 by the
American Chemical Society
A New Family of Polymerizable Lyotropic Liquid Crystals: Control
of Feature Size in Cross-Linked Inverted Hexagonal Assemblies via
Monomer Structure
Mary A. Reppy,*,§ David H. Gray,‡ Brad A. Pindzola, Juston L. Smithers, and
Douglas L. Gin*
Contribution from the Department of Chemistry, UniVersity of California, Berkeley, California 94720-1460
ReceiVed July 6, 2000
Abstract: An efficient and versatile synthesis of a series of polymerizable amphiphilic mesogens that affords
control over tail length and position of the polymerizable group is described. The synthesis employs a novel
and facile method of preparing styrene ethers. The monomers are sodium salts of styrene ether-modified fatty
acids that can be used to form cross-linkable inverted hexagonal (HII) lyotropic liquid crystal (LLC) phases at
ambient temperature with controllable nanometer-scale dimensions. Examination of a series of regioisomers
with the same alkyl chain length but with the styrene ether group at different locations along the chain revealed
that the position of the styrene ether has a profound effect on the dimensions of the resulting HII phase at a
fixed temperature and composition. Increasing overall monomer tail length also has a significant, although
smaller, effect on the unit cell dimensions of the LLC phase. By controlling the structure of the LLC monomer
in this manner, cross-linked HII phases with interchannel distances (ICD) ranging from 29 to 54 Å can be
obtained. Furthermore, changing the counterion from Na+ to tetraalkylammonium ions leads to further expansion
of the HII unit cell to a maximum ICD of 65 Å, as well as to the production of a lamellar phase. Use of these
monomers affords a new and unparalleled degree of control over phase structure and dimensions for the
production of nanostructured organic materials.
Introduction
derstand the basics of performing chemistry and engineering
on the nanometer size regime.3 Many of the techniques used to
obtain this degree of order in synthetic systems are based on
the phenomenon of molecular self-assembly: that is, the intrinsic
ability of certain chemical systems to spontaneously organize
into ordered arrays on the nanometer or micrometer scale.4
The synthesis of materials with architectural control on the
nanometer scale is arguably one of the greatest current chal-
lenges in the area of materials chemistry.1 While Nature has
mastered the art of synthesizing materials with that level of
sophistication,2 materials chemists are only beginning to un-
* To whom correspondence should be addressed.
(3) (a) Calvert, P. Mater. Sci. Eng. 1994, C1, 69. (b) Peppas, N. A.;
Langer, R. Science 1994, 263, 1715. (c) Heuer, A. H.; Fink, D. J.; Laraia,
V. J.; Arias, J. L.; Calvert, P. D.; Kendall, K.; Messing, G. L.; Blackwell,
J.; Rieke, P. C.; Thompson, D. H.; Wheeler, A. P.; Veis, A.; Caplan, A. I.
Science 1992, 255, 1098.
§ Present address: Analytical Biological Services Inc., 701-4 Cornell
Business Park, Wilmington, DE 19801.
‡ Present address: Department of Chemistry, De Anza College, 21250
Stevens Creek Blvd., Cupertino, CA 95014.
(1) For recent perspectives on nanometer-scale materials, see the articles
in the following special journal issues dedicated to this topic: (a) Chem.
ReV. 1999, 99, 9. (b) Science 1997, 277. (c) Chem. Mater. 1996, 8.
(2) Addadi, L.; Weiner, S. Angew. Chem., Int. Ed. Engl. 1992, 31, 153.
(4) For recent reviews of nanostructure synthesis by self-assembly, see:
(a) Kazmaier, P.; Chopra, K. MRS Bull. 2000, 25 (4), 30. (b) Mio, M. J.;
Moore, J. S. MRS Bull. 2000, 25 (4), 36. (c) Stupp, S. I.; Pralle, M. U.;
Tew, G. N.; Li, L.; Sayer, M.; Zubarev, E. R. MRS Bull. 2000, 25 (4), 42.
10.1021/ja002462i CCC: $20.00 © 2001 American Chemical Society
Published on Web 12/30/2000

364 J. Am. Chem. Soc., Vol. 123, No. 3, 2001
Reppy et al.
and most recently catalytic organic analogues of zeolites20 have
been prepared using polymerizable LLCs as building blocks.
The inverted hexagonal (HII) phase, in particular, has been
employed as a preferred template for many of these new
systems.11,13,14-17,20 Cross-linking of the HII phase affords a
robust organic matrix with ordered, one-dimensional nanochan-
nels that can be used for applications such as macromolecular
exclusion or filtration, or as the basis for anisotropic nanocom-
posites if the channels are filled with reinforcing materials.
Recent work in our group has shown that condensed organic
and inorganic materials formed within cross-linked HII as-
semblies exhibit properties not observed in the analogous bulk
materials.14,17 In addition, the organization of the ionic head-
groups in these systems affords nanochannels with unusual
chemical environments. For example, cross-linked HII phases
of carboxylate-containing monomers were found to have
nanochannels with enhanced basicity that are capable of
heterogeneous base catalysis and substrate size exclusion.20
Figure 1. Representations of some common LLC phases formed by
amphiphiles in the presence of water.
Langmuir-Blodgett films,5 liquid-crystalline (LC) polymers,6
and microphase-separated block copolymers7 are examples of
such systems that have been used as templates for the formation
of nanostructured materials with interesting properties. Another
very promising and versatile approach is the use of polymer-
izable lyotropic liquid crystal (LLC) assemblies as template
media.
One of the major advantages of using polymerizable LLC
templates over other self-assembly methods is the power to
modulate the nanometer-scale dimensions and geometry of the
resulting materials by simply altering the temperature or
composition of the system, or the structure of the monomeric
building blocks.8 The LLC behavior can be explained by
considering the energetics of the amphiphiles as a collective
ensemble, and/or the molecular shape of the constituent am-
phiphiles. Using the first theory, changes in LLC phase
dimensions and geometry with variations in temperature and
water content can be explained by considering the interfacial
energy and intrinsic curvature of the systems.21 Gruner and co-
workers have shown that the structural dimensions of the HII
phase can be systematically modulated by varying system
temperature.22 However, at a fixed temperature and system
composition, it has been proposed that the “shape” of the
amphiphile has the more important role in determining which
mesophase a LLC mixture will tend to adopt.9 In an effort to
create a simplified tie between amphiphile structure and
preferred phase geometry under these conditions, Israelachvili9
formulated an expression termed the “critical packing param-
eter,” Q ) V/a0lc. This expression relates the ratio of the volume
of the organic portion of the mesogen (V), the area of the
amphiphilic headgroup (a0), and average critical length (lc) to
the expected curvature, and thus geometry, of the various
mesophases. For example, amphiphiles with a tapered shape
(i.e., a small hydrophilic headgroup and a broad, flattened
hydrophobic tail section) tend to form the HII phase, whereas
amphiphiles with a cylindrical shape tend to pack into low-
curvature lamellar (L) phases. By modulating the size of the
headgroup and varying the length and breadth of the hydro-
phobic tails, the unit cell dimensions of the preferred LLC phase
or even the phase itself can be altered, depending on the
magnitude of the changes to the monomer. For example, we
have recently demonstrated that in the case of sodium 3,4,5-
tris(11′-acryloyloxyundecyloxy)benzoate, which has a distinct
tapered shape, the unit cell dimensions of the resulting HII phases
can be tuned by changing the metal counterion on the head-
LLCs are amphiphilic molecules that spontaneously assemble
in the presence of water to form phase-segregated assemblies
with specific geometries and regular nanometer-size features
(Figure 1).8 The type of LLC phase formed depends on the
concentration of the mesogen,8 the temperature of the system,8
and the shape of the mesogen itself.9 LLC assemblies are
intrinsically fluid in nature; thus, their ordered structures are
easily distorted or disrupted by physical and chemical forces.
To overcome this problem for the construction of robust
materials, polymerizable or cross-linkable LLCs have been
developed.10 These reactive amphiphiles aggregate into the same
types of assemblies as their nonpolymerizable analogues but
the molecules can be covalently linked to their nearest neighbors
in situ to form highly stable polymer networks with retention
of the original microstructure.
Polymerizable LLC phases have recently been used to
demonstrate that nanostructured organic materials with novel
or enhanced properties can be synthesized. For example,
nanoporous organic polymers,11-13 ordered nanocomposites,14-19
(d) Brunsveld, L.; Folmer, B. J. B.; Meijer, E. W. MRS Bull. 2000, 25 (4),
49. (e) Hawker, C. J.; Hedrick, J. L.; Miller, R. D.; Volksen, W. MRS Bull.
2000, 25 (4), 54. (f) Lehn, J.-M. Pure Appl. Chem. 1994, 66 (10/11), 1961.
(g) Whitesides, G. M.; Mathias, J. P.; Seto, C. T. Science 1991, 254, 1312.
(5) Litvin, A. L.; Valiyaveettil, S.; Kaplan, D. L.; Mann, S. AdV. Mater.
1997, 9, 124.
(6) Nelson, E. J.; Samulski, E. T. Mater. Sci. Eng. 1995, C2, 133.
(7) (a) Zhao, D.; Feng, J.; Huo, Q.; Melosh, N.; Frederickson, G. H.;
Chmelka, B. F.; Stucky, G. D. Science 1998, 279, 548. (b) Kraemer, E.;
Foerster, S.; Goeltner, C.; Antionetti, M. Langmuir 1998, 14, 2027.
(8) For reviews of LLCs and their phases, see: (a) Tiddy, G. J. T. Phys.
Rep. 1980, 57, 1. (b) Seddon, J. M. Biochim. Biophys. Acta 1990, 1031, 1.
(9) Israelachvili, J. N. Intermolecular and Surface Forces with Applica-
tions to Colloidal and Biological Systems; Academic: London, 1985; pp
249-257.
(10) For reviews of nanostructured materials synthesis using polymer-
izable LLCs, see: (a) Miller, S. A.; Ding, J. H.; Gin, D. L. Curr. Opin.
Colloid Interface Sci. 1999, 4, 338. (b) O’Brien, D. F.; Armitage, B.;
Benedicto, A.; Bennett, D. E.; Lamparski, H. G.; Lee, Y.-S.; Srisiri, W.;
Sisson, T. M. Acc. Chem. Res. 1998, 31, 861. (c) Ringsdorf, H.; Schlarb,
B.; Venzmer, J. Angew. Chem., Int. Ed. Engl. 1988, 27, 113.
(11) Herz, J.; Reiss-Husson, F.; Rempp, P.; Luzzati, V. J. Polym. Sci.,
Part C 1963, 4, 1275.
(12) Lee, Y.-S.; Yang, J.-Z.; Sisson, T. M.; Frankel, D. A.; Gleeson, J.
T.; Aksay, E.; Keller, S. L.; Gruner, S. M.; O’Brien, D. F. J. Am. Chem.
Soc. 1995, 117, 5573.
(13) Srisiri, W.; Sisson, T. M.; O’Brien, D. F.; McGrath, K. M.; Han,
Y.; Gruner, S. M. J. Am. Chem. Soc. 1997, 119, 4866.
(14) Smith, R. C.; Fischer, W. M.; Gin, D. L. J. Am. Chem. Soc. 1997,
119, 4092.
(17) Gray, D. H.; Gin, D. L. Chem. Mater. 1998, 10, 1827.
(18) Sellinger, A.; Weiss, P. M.; Nguyen, A.; Lu, Y.; Assink, R. A.;
Gong, W.; Brinker, C. J. Nature 1998, 394, 256.
(19) Werkman, P. J.; Wieringa, R. H.; Schouten, A. J. Thin Solid Films
1998, 323, 251.
(15) Gray, D. H.; Hu, S.; Juang, E.; Gin, D. L. AdV. Mater. 1997, 9,
731.
(20) Miller, S. A.; Kim, E.; Gray, D. H.; Gin, D. L. Angew. Chem., Int.
Ed. 1999, 38, 3021.
(16) Deng, H.; Gin, D. L.; Smith, R. C. J. Am. Chem. Soc. 1998, 120,
3522.
(21) Gruner, S. M. J. Chem. Phys. 1989, 93, 7562.
(22) Tate, M. W.; Gruner, S. M. Biochemistry 1989, 28, 4245.

A New Family of Polymerizable Lyotropic Liquid Crystals
J. Am. Chem. Soc., Vol. 123, No. 3, 2001 365
group16 and/or the length of the three aliphatic tails.23 Also,
below a certain tail length the monomer adopts the L phase.
Herein, we present an efficient, versatile synthesis of a series
of regiopure, styrene ether analogues of 1 (compounds 2-11)
that affords control over both overall tail length and position
of the polymerizable group. By varying these parameters in a
systematic fashion, we have been able to elucidate the effect of
these changes on HII phase formation at constant temperature
for this class of monomers based on styrene-substituted, long-
chain carboxylic acid salts.25 Variation of three key structural
parameterssthe tail length, the point of the styrene ether
attachment, and the counterion of the headgroupsresulted in a
series of polymerizable LLCs. These LLCs were combined with
H2O and DVB at ambient temperature to produce cross-linked
HII phases with tunable interchannel distances (ICDs) in the
29-65 Å range. Theoretical studies based on neutron-scattering
experiments suggest that the inner diameter of the water channels
of the HII phase is directly proportional to the ICD,8b thus control
over the ICD implies control over the size domain of the reactive
aqueous regions. Manipulation of the feature size of the HII
phase should lead to the ability to selectively tune the properties
of nanostructured materials prepared from these phases.
The potential for control of phase architecture and dimensions
in these nanostructured systems through monomer design is quite
remarkable. However, at this point only loose guidelines for
controlling or predicting LLC mesophases have been elucidated
from the observed relationships between amphiphile structure
and the properties of the resulting LLC assemblies. Furthermore,
some LLC systems are comprised of mixtures of several
isomers, yet still form highly ordered phases. Consequently in
these systems, the structural factors that direct the formation of
one phase over another and influence the unit cell dimensions
are not clearly understood.
One important example of such a system is salts of styrene-
substituted, long-chain carboxylic acids. These polymerizable
amphiphiles adopt highly ordered HII phases even though they
do not possess a distinct taper shape. In 1963, Luzzati and co-
workers first showed that an isomeric mixture of calcium
p-styrylundecanoates derived from 10-undecenoic acid form an
HII phase at room temperature and can be cross-linked with
retention of microstructure by copolymerizing the monomer with
moderate amounts (5-20%) of divinylbenzene (DVB).11 Fol-
lowing the work of Luzzati, our group developed a similar HII
forming monomer system, the sodium salt of the styryl
derivative of 9-octadecenoic (i.e., oleic) acid (1).15,17 Mixtures
Results and Discussions
Synthesis of Regiopure Styrene Ether Analogues of 1. To
make a homologous series of single regioisomer analogues of
1, it was desirable to have a short and modular synthetic route.
The key synthetic step required is the attachment of a styrene
group at a specific position along the fatty acid chain. Phenyl
rings have been attached to unsaturated chains by Friedel-Crafts
coupling24a,26 and then elaborated to the styrene via the
corresponding acetophenones or benzaldehydes. Unfortunately,
as discussed above, Friedel-Crafts couplings have been shown
to lead to mixtures of regioisomers, arising from rearrangement
of the carbocation intermediates. It is also possible to create
regiospecific isomers of the phenyl-branched fatty acid via
addition of a phenyl Grignard reagent to a ketone/fatty acid, or
by adding an alkyl Grignard to a fatty acid terminated with a
phenyl ketone,26 with subsequent reduction of the alcohol to a
methine. The phenyl group must then be transformed to the
styrene; overall these routes to individual isomers are too long
for efficient synthesis of multiple regioisomers and homologues
of 1.
Introduction of an ether linkage between the styrenic moiety
and the fatty acid backbone significantly simplifies the regiospe-
cific synthetic route. An alternative to direct attachment of a
styrene moiety to the chain is the use of a phenolic or benzylic
ether linkage to give styrene or styryl ethers. Styrene ethers
have been prepared by coupling either 4-hydroxybenzaldehyde27
or 4-hydroxyacetophenone28 to an alcohol using the Mitsunobu
reaction and then transforming the carbonyl group into a vinyl
of 1, water, and DVB can be photopolymerized with retention
of phase to serve as templates for nanocomposite15,17 and
heterogeneous catalyst formation.20 Transition-metal and alkaline
earth salts were also prepared from 1 by ion exchange. The
cadmium salt was used for CdS formation in the aqueous
channels of the HII phase, giving nanoparticles with diameters
of 40 Å or less.17
Unfortunately, 1 exists as a complex mixture of regioisomers
with the styrene group located at different positions along the
18-carbon backbone.15 A key step in the synthesis of 1 is the
Friedel-Crafts reaction of methyl oleate and benzene. During
this step, the carbocation in the intermediate migrates up and
down the chain. This results in a mixture of isomers with the
phenyl ring (i.e., the styryl moiety) attached anywhere from the
sixth carbon to the seventeenth carbon of the chain,24 with no
single isomer representing more than 20% of the mixture.
Traditionally, LLC phases have been made with a single
surfactant species, allowing aspects of mesogen shape to be
correlated with the phase formed. Although 1 is a versatile
platform for making functional nanostructured materials, its
complex regioisomeric makeup makes it difficult to identify the
structural factors that influence the formation of the HII phase.
In addition, these factors also make it difficult to control the
unit cell dimensions of the LLC assembly via systematic
monomer modification.
(25) Although it is known that the dimensions of the HII phase are also
affected by temperature (see ref 22), this paper only presents the effects of
molecular structure on LC phase architecture at constant temperature (24
( 1 °C) for this class of monomers. Preliminary studies showed that
temperature changes of ca. 10 °C are necessary before changes in lattice
dimension of g0.5 Å are observed in our systems (see Supporting
Information). Thus, the variations in the HII dimensions within the (1 °C
window of error in our measurements can be considered very small and
near the limit of accuracy for our X-ray diffractometer in the low-angle
region. The effect of temperature on the LC phases of these monomers
will be a subject of future investigation.
(26) Freedman, H. H.; Mason, J. P.; Medalia, A. I. J. Org. Chem. 1958
23, 76.
(27) Baena, M. J.; Barbera´, J.; Espinet, P.; Ezcurra, A.; Ros, M. B.;
Serrano, J. L. J. Am. Chem. Soc. 1994, 116, 1899.
(28) Malamas, M. S.; Carlson, R. P.; Grimes, D.; Howell, R.; Glaser,
K.; Gunawan, I.; Nelson, J. A.; Kanzelberger, M.; Shah, U.; Hartman, D.
A. J. Med. Chem. 1996, 39, 237.
(23) Gin, D. L.; Gray, D. H.; Smith, R. C. Synlett 1999, 10, 1509.
(24) (a) Harrison, W. J.; McDonald, M. P.; Tiddy, G. J. T. J. Phys. Chem.
1991, 95, 4136. (b) Smith, F. D.; Stirton, A. J. J. Am. Oil Chem. Soc. 1971,
48, 160.

366 J. Am. Chem. Soc., Vol. 123, No. 3, 2001
Reppy et al.
Scheme 1
group.29 Alternatively, 4-chlorostyrene has been used to func-
tionalize poly(ethylene glycol) at 70 °C with KOH.30 The
secondary alcohols used in our synthetic route were unreactive
with styryl chloride, bromide, or iodide; thus, the Mitsunobu
reaction was used to form the ether linkage.
benzaldehyde were found to proceed in higher yields of 70-
80%. It seemed likely that 4-vinylphenol was less reactive than
the carbonyl-substituted phenols due to the lower acidity of
4-vinylphenol. To address this issue, 1,1′-(azodicarbonyl)-
dipiperdine (ADDP) and tributylphosphine in toluene were
substituted for DIAD and triphenylphosphine in THF, following
the work of Tsunoda et al.37 with acidic carbon compounds in
Mitsunobu couplings. These conditions have not been previously
used for the formation of alkyl aryl ethers. Using this procedure,
the desired styrene ethers 29-38 were produced in 75-85%
isolated yields (Scheme 2). Hydrolysis of 29-38 to the
corresponding acids 39-48 followed by neutralization with
NaOH subsequently yielded the sodium salts 2-11.
The route to the styrene ethers, 2-11, proceeded via the
secondary alcohol/esters (12-21). The alcohols were prepared
by three different routes, as shown in Scheme 1. The secondary
alcohols 12-15, 17, 18, 20, and 21 were synthesized by first
esterifying the commercially available ω-hydroxy fatty acids
or corresponding lactones, and then oxidizing the resulting
ω-hydroxy esters (22-24) to the corresponding aldehydes (25-
27).31,32 Addition of n-alkyl Grignard reagents to the crude
aldehydes afforded the secondary alcohols as racemic mixtures,
with the individual positions of the hydroxy groups determined
by the choice of starting fatty acids and alkyl Grignard reagents.
Alcohol 16 was made in one step by esterification of com-
mercially available 12-hydroxystearic acid. Alcohol 19 was
formed by coupling a tetradecanyl Grignard cuprate with an
acid chloride to form the ketone (28),33 followed by reduction
of 28 to 19 with NaBH4.
Initial attempts to attach the styrene ether onto the secondary
alcohols 12-21 via the Mitsunobu reaction34,35 with 4-vinylphe-
nol using triphenylphosphine and diisopropylazodicarboxylate
(DIAD) in THF only afforded the desired products in modest
yields (50-60%). Unfortunately, variation of the reaction
temperature, reaction time, and order of addition did not lead
to significant improvements in yield.36 However, Mitsunobu
couplings with both 4-hydroxyacetophenone and 4-hydroxy-
It should be noted that the success of this method has wider
implications in monomer synthesis than its application to this
particular series of compounds. The Mitsunobu reaction is
tolerant of a wide variety of functional groups.35,36 Thus, the
development of this general method for making styrene ethers
makes the attachment of a styrene group as facile as attaching
an acrylate or any of the other common ester-based polymer-
izable groups. This reaction quickly converts primary and
secondary alcohols to polymerizable styrene ether moieties with
inversion of chirality at the alcohol carbon. This transformation
allows the styrene group to be used in situations where the ester-
based polymerizable groups are less desirable or unsuitable.
Using this synthetic route, it was possible to prepare the 10
polymerizable LLC salts 2-11 with overall chain lengths from
12 to 22 carbons, and with the styrene ether moiety located in
a variety of positions along the chain (referred to herein as
“branch points”). The 12- and 16-carbon linear styrene ether
salts 49 and 50 were prepared in a similar manner from 22 and
23 by modified Mitsunobu coupling to form the terminal styrene
ethers (51, 52), followed by de-esterification (53, 54) and
formation of the sodium salts (Scheme 2). The identities of all
(29) Piskala, A.; Rehan, A. H.; Schlosser, M. Collect. Czech. Chem.
Commun. 1983, 48, 3539.
(30) Stowe, S. C. U.S. Patent 3,190,925, 1965.
(31) Cheng, Y. S.; Liu, W. L.; Chen, S. H. Synthesis 1980, 223.
(32) Piancatelli, G.; Scettri, A.; D’Auria, M. Synthesis 1982, 245.
(33) Bergbreiter, D. E.; Killough, J. M. J. Org. Chem. 1976, 41, 2750.
(34) Manhas, M. S.; Hoffman, W. H.; Lai, B.; Bose, A. K. J. Chem.
Soc., Perkin Trans. 1 1975, 461.
1
new styrene ether compounds were confirmed by IR, H ,and
(35) Mitsunobu, O. Synthesis 1981, 1.
(36) Hughes, D. L. Org. React. 1992, 42, 335.
(37) Tsunoda, T.; Yamamiya, Y.; Ito, S. Tetrahedron Lett. 1993, 34,
1639.

A New Family of Polymerizable Lyotropic Liquid Crystals
J. Am. Chem. Soc., Vol. 123, No. 3, 2001 367
Scheme 2
Table 1. Influence of Alkyl Tail Length and Styrene Ether
Position on the Dimensions of the HII Phases Formed by Neat LLC
Sodium Salt Monomers 2-11 (Unpolymerized)d
13C NMR and elemental analysis or high-resolution mass
spectrometry. The LLC phases of the salts were characterized
by polarized light microscopy (PLM) and X-ray diffraction
(XRD), both in the neat form and as mixtures with water, DVB,
and 2 wt % 2-hydroxy-2-methylpropiophenone (HMPP) incor-
porated as a photoinitiator.15 The LLC mixtures were then
photopolymerized and characterized again. All the LLC phases
were prepared and studied at ambient temperature (24 ( 1 °C).
Effect of Monomer Structure on LLC Phase Dimensions.
Low-angle XRD and PLM analysis of monomers 2-11 revealed
that they all form the HII phase at ambient temperature in neat
form and when mixed with 6 wt % H2O, 10 wt % DVB, and 2
wt % HMPP; however, 5 also shows some evidence of the L
phase in addition to the HII phase. The optical textures of 2-4
and 6-11 showed the characteristic kaleidoscopic textures of
the hexagonal phases, and the positions of their observed XRD
peaks were consistent with that of a hexagonal LLC phase (1,
1/x3, 1/2, 1/x7, ... corresponding to d100, d110, d200, d210, ...)8b,38
(see Supporting Information for listings of all XRD data). The
average interchannel distances (ICDs)8b,38 were calculated from
the average calculated d100 value ( d100 ) based on all observed
XRD peaks39 (i.e., ICD ) d100 /cos 30°) (see Table 1). As
expected, there is a rough correlation between monomer chain
length and ICD, with longer chains leading to larger ICDs. A
more striking observation is that the position of the styrene ether
branch point along the monomer chain has a strong effect on
the ICD of the HII phase formed, as illustrated by the five neat
octadecanoate isomers 5-9 (Table 1). Figure 2 shows the XRD
profiles of the HII phases of neat 5, 7, and 9 taken at 24 ( 1
HII phase
LLC
no. of C
position of styrene
monomer in alkyl tail ether attachmenta
d100 (Å)b ICD (Å)
2
3
4
5
6
7
8
9
10
11
12
12
16
18
18
18
18
18
22
22
C10
C6
C10
C16
C12
C10
C6
C4
C16
C10
35.1
24.9
32.8
44.6c
35.6
35.3
29.3
30.3
46.2
38.4
40.5
28.7
37.9
51.5c
41.1
40.8
33.8
35.0
53.3
44.3
a Carbon position for styrene ether attachment numbered progres-
b
sively along the alkyl tail with C1 being the carboxylate carbon. d100
is the average value of d100 based on the positions of all the XRD peaks
observed for the HII phase (see ref 39 and the Supporting Information).
c Evidence of a small amount of L phase formation in the HII phase.
d X-ray diffraction measurements on the HII phases were performed at
24 ( 1 °C.
°C, showing the shift in the measured d100 values with the
changes in isomer structure. In general, the closer the styrene
ether branch point is to the end of the tail, the larger the observed
ICD of the resulting HII phases. It can be seen that this trend
holds for the dodecanoate and docosanoate isomers as well, with
the ICDs of the HII phases of the neat sodium salts spanning
29-54 Å. The longer chain isomers generally form HII phases
with larger ICDs than their shorter counterparts. However, of
the two variables, chain length and position of polymerizable
group, the latter has the stronger effect upon LLC phase
dimensions. When the branch point is near the headgroup (i.e.,
monomers 8 and 9), the ICDs are reduced, and only the d100
peak has a strong intensity, suggesting a more disordered phase.
In contrast to the branched salts, the linear sodium salts with
the styrene ether group at the terminus of the alkyl chain (49,
50) are crystalline and hydrophobic. Comparing the behavior
(38) Resel, R.; Thiessl, U.; Gadermaier, C.; Zojer, E.; Kriechbaum, M.;
Amenitsch, H.; Gin, D.; Smith, R.; Leising, G. Liq. Cryst. 2000, 27, 407.
(39) Because of large changes in d spacing with small changes in 2θ in
the low-angle region of the XRD spectrum, the primary peak d100 is often
more accurately determined by averaging d100 values calculated from the
positions of all the peaks in the spectrum: d100 ) [(d100‚1) + (d110‚x3)
+ (d200‚x4) + (d210‚x7) + ...]/n, where n ) the total number of observed
XRD peaks for a hexagonal phase. Similarly, ICD is calculated from the
d100 value (ICD ) d100 /cos 30°). See: Johannson, G.; Percec, V.; Ungar,
G.; Zhou, J. P. Macromolecules 1996, 29, 646.

368 J. Am. Chem. Soc., Vol. 123, No. 3, 2001
Reppy et al.
Figure 3. Representative FT-IR spectra of a HII mixture of 4/DVB/
H2O/HMPP (82/10/6/2 w/w/w/w): (a) before photopolymerization and
(b) after photopolymerization.
Figure 2. XRD profiles of the HII phases of three unpolymerized neat
monomers taken at 24 ( 1 °C: (a) 5, (b) 7, and (c) 9.
of 50 to that of 5, it can be seen that addition of just an ethyl
group as a branch is sufficient to break up strong crystalline
packing and induce LC behavior at room temperature. This
observation is consistent with previous work on branched
surfactants.40 It should also be noted that for the neat LLC
octadecanoate salt series 5-9, placement of the styrene ether
branch point very close to the terminus of the tail also begins
to favor some formation of the L phase (Table 1).
The samples mixed with 6 wt % H2O, 10 wt % DVB, and 2
wt % HMPP were photopolymerized with 365 nm light for 12-
16 h at ambient temperature (24 ( 1 °C). The extent of
polymerization was comparable to that of 1 (ca. 80%), as
measured by FT-IR spectroscopy (Figure 3).15 The resulting
cross-linked polymers are slightly opaque, hard, free-standing
materials that can be ground to a fine powder. They are also
completely insoluble in common organic solvents and water and
do not exhibit any noticeable swelling. The cross-linked samples
retain the HII phase as determined by PLM, and also exhibit
XRD peaks characteristic of the HII phase (see Figure 4 and
Table 2). The HII structure of the polymerized samples persists
even at temperatures well in excess of 100 °C with only slight
changes in unit cell dimensions (see Supporting Information).
The XRD secondary peaks of polymerized mixtures from 8 and
9 were weakened significantly compared to the unpolymerized
mixtures, and in the case of 9 effectively disappeared. The
success of the photopolymerization showed that the individual
styrene ether isomers 2-11 can be used in the place of 1, to
make functionalized organic nanomaterials. Phenyl ethers are
stable to a wide variety of chemical conditions, being signifi-
cantly labile only in the presence of powerful Lewis acids and
Figure 4. XRD profiles of the HII phases of (a) neat 4; (b) a mixture
of 4/DVB/H2O/HMPP (82/10/6/2 w/w/w/w) before photopolymeriza-
tion; and (c) a mixture of 4/DVB/H2O/HMPP (82/10/6/2 w/w/w/w)
after 12 h of photopolymerization. The samples were all analyzed at
ambient temperature (24 ( 1 °C).
concentrated protic acids,41 so the polymerized matrices could
be used under a range of conditions for heterogeneous catalysis,
as templates for composite materials, and for nanoparticle
formation.
Further studies were conducted on a selection of the LLC
isomers. Three of the octadecanoate isomers, 5, 7, and 9, were
chosen. The effects on the phase of adding H2O to the sodium
salts were measured, and the results compared to those
determined earlier for the styryl isomeric mix 1 (Table 3).
Variation of the percentage of water added to HII phases is
known to affect the diameter of the aqueous channels8b and
hence is another possible avenue for control of the nanodimen-
sions. It can be seen that of the three octadecanoate isomers,
(41) (a) Sala, T.; Sargent, M. V. J. Chem. Soc., Perkin Trans. 1 1979,
2593. (b) Greene, T. W.; Wuts, P. G. M. ProtectiVe Groups in Organic
Synthesis, 2nd ed.; John Wiley & Sons: New York, 1991; pp 426-427.
(40) Winsor, P. A. In Liquid Crystals and Plastic Crystals; Gray. G.
W., Winsor, P. A., Eds; Ellis Horwood: London, 1974; Vol. I, p 253.

A New Family of Polymerizable Lyotropic Liquid Crystals
J. Am. Chem. Soc., Vol. 123, No. 3, 2001 369
Table 2. Influence of Alkyl Tail Length and Styrene Ether
Position on the Dimensions of the HII Phases of LLC Monomers
2-11 Formed with 6 wt % H2O, 12 wt % DVB, and 2 wt %
HMPP, and Photopolymerizedd
specific isomers to accommodate more DVB cross-linker while
retaining the HII phase is of particular interest, as the addition
of higher percentages of DVB may lead to even more robust
materials.
cross-linked HII phase
d100 (Å)b ICD (Å)
It is clear from the studies of the styrene ether fatty acid
sodium salts that changing the location of the branch point and
overall tail length (and hence the alkyl tail volume) generally
does not cause the salts to form phases other than the HII phase.
Only one of the isomeric LLC sodium salts (5) displays any
tendency to form the L phase. Furthermore, the phase behavior
of the individual octadecanoate styrene ether isomers 5, 7, and
9 with H2O and DVB (Table 3) suggests that the LLC behavior
of the styryl regioisomeric mixture 1 is dominated by the more
abundant isomers, which have the polymerizable units near the
middle of the alkyl chains.24 To initially examine the effect of
varying the headgroup size, tetramethylammonium salts (55-
58) were made from styrene ether fatty acids 40, 42, 44, and
LLC
no. of C
position of styrene
monomer in alkyl tail ether attachmenta
2
3
4
5
6
7
8
9
10
11
12
12
16
18
18
18
18
18
22
22
C10
C6
C10
C16
C12
C10
C6
C4
C16
C10
34.6
25.3
31.8
42.9c
36.7
34.5
32.7
34.1
46.3
37.9
39.9
29.2
36.8
49.6c
42.4
39.8
37.8
39.4
53.5
43.7
a Carbon position for styrene ether attachment numbered progres-
b
sively along the alkyl tail with C1 being the carboxylate carbon. d100
is the average value of d100 based on the positions of all the XRD peaks
observed for the HII phase (see ref 39 and the Supporting Information).
c Evidence of a small amount of L phase formation in the HII phase.
d The phases were cross-linked at 24 ( 1 °C, and X-ray diffraction
measurements on the HII networks were all performed at 24 ( 1 °C.
Table 3. Variation of LLC Phase Structure of Selected LLC
Monomers as a Function of Water Contentd
structure of LLC phases with different amts of H2O
[phase, ( d100 (Å))]a
LLC
monomer
0% H2O
6% H2O
12% H2O
24% H2O
HII (38.3)b
L (47.9)
46 for further examination of the effects of adding a large
headgroup. Up to 50 wt % H2O was added to the salts and the
phases characterized at ambient temperature (24 ( 1 °C). All
the tetramethylammonium salts formed L phases, as expected
from the Israelachvili model.9 A tetraethylammonium salt of
42 (59) was also prepared. It adopted an HII phase when mixed
with 6 and 12 wt % H2O (ICD of 65 Å), then formed the L
phase when mixed with 24 wt % H2O.
1
5
7
9
HII (37.6)
-c (44.6)
HII (35.3)
HII (30.3)
HII (37.9)
L (48.2)
HII (34.7)
HII (28.6)
HII (38.7)
L (48.2)
HII (32.9)
HII (28.6)
HII (33.0)
-c (28.7)
a
d100 is the average value of d100 based on the positions of all the
XRD peaks observed for each phase. b Formed with 20 wt % water.
c Mixture of HII and L phases. d X-ray diffraction measurements were
all performed at 24 ( 1 °C.
the one with the styrene ether moiety in the middle of the alkyl
tail (7) exhibits the most stable HII phase with respect to
increasing water content. In this regard, 7 is most similar to 1
with respect to resistance to changes in phase structure with
changes in system composition. The monomer with the styrene
ether unit closest to the ionic headgroup (9) maintains the HII
phase until 24 wt % added water is reached, at which point it
forms a mixture of HII and L phases. In contrast, monomer 5,
with the styrene ether branch point closest to the end of the
alkyl tail, seems to be the most sensitive to changes in water
content. Addition of even small amounts of water to the mixed
LLC phase of 5 (predominantly HII with some L phase) at
ambient temperature changes the phase entirely to an L phase.
Thus, depending on the structure of the LLC monomer salt,
the amount of added water affects the type of LLC phase favored
at ambient temperature but only has a small effect on the lattice
dimensions ((1 Å) within each LLC phase formed. A similar
experiment was performed by adding a mixture of 83 wt %
DVB and 17 wt % HMPP. The samples were analyzed,
photopolymerized, and analyzed again. Monomer 7 tolerated
20 wt % added DVB/HMPP and retained the HII phase upon
polymerization. Indeed, the order in the HII phase of 7 appears
to improve upon polymerization. Upon addition of the same
amount of DVB/HMPP to neat 5 at ambient temperature, it
maintained the original mixed HII/L phase and was able to retain
the mixed phase microstructure upon photopolymerization. In
contrast, the LLC phase formed from 9 significantly deteriorated
upon polymerization (see Supporting Information). This is
consistent with the behavior of 9 when mixed with 12 wt %
DVB/HMPP and 6 wt % H2O and polymerized. The ability of
Conclusions
A new family of polymerizable LLCs has been prepared using
a novel and versatile method for synthesizing styrene ethers.
This homologous series of the sodium salts of styrene ether-
modified fatty acids has been employed in the formation of
cross-linkable HII phases with control of phase dimensions.
Examination of a subseries of regioisomers with the same overall
chain length showed that the relative position of the styrene
ether group along the alkyl chain has a profound effect upon
the dimensions of the HII phase at a fixed temperature and
system composition. Placing the styrene ether closer to the chain
end and further from the headgroup leads to HII phases with
systematically larger ICDs, but with a slight concomitant
increase in tendency to form the L phase. Varying the total chain
length of the monomer also has a significant, though smaller,
effect on the unit cell dimensions of the LLC phases, with longer
chains affording larger ICDs. Furthermore, changing the coun-
terion on the monomers from Na+ to tetraalkylammonium ions
leads to further control of the unit cell dimensions. These effects
in combination allow the formation of cross-linked HII phases
at ambient temperature with tunable ICDs in the 29-65 Å range.
Manipulation of monomer structure in this fashion offers a new
and unparalleled degree of control over feature size in the
production of nanostructured organic catalysts and composites
based on polymerizable LLC assemblies. In these systems, such
control can be used to modulate substrate size exclusion in
nanoporous catalyst design, or to form nanoparticles of con-
trolled size in nanocomposite synthesis. Our group is currently
engaged in studying the catalytic properties of these cross-linked

370 J. Am. Chem. Soc., Vol. 123, No. 3, 2001
Reppy et al.
Methyl 10-Oxodecanoate (26).45 PCC/Al2O3 (20.9 g, 17.0 mmol)
and 3 (1.908 g, 9.43 mmol) were combined. The flask was then
evacuated and filled with Ar, and anhydrous CH2Cl2 (20 mL) was
added. The reaction mixture was stirred at ambient temperature for 5
h and then diluted with diethyl ether (60 mL). The mixture was then
filtered through a ca. 4 cm plug of Florisil with extensive washing
with diethyl ether (170 mL). The solvent was removed under partial
pressure and the resulting oil dried in vacuo to a constant weight of
1.652 g (88% yield). Spectral data were consistent with those reported
in the literature.45
Methyl 10-Hydroxyoctadecanoate (17).46 Anhydrous THF (20 mL)
was added to 4 (1.250 g, 6.24 mmol) under Ar and the solution chilled
to 0 °C. Octylmagnesium bromide, 2.0 M in diethyl ether (4.0 mL, 8.0
mmol), was added, and the reaction was stirred at 0 °C for 1 h. After
quenching with H2O (5 mL) and 1 M HCl (15 mL), the mixture was
extracted with diethyl ether (2 × 50 mL). The combined organic layers
were then washed with 1 M HCl (1 × 15 mL) and saturated NaCl (2
× 15 mL), and then dried over MgSO4. After removal of the solvent
under partial pressure, the product was dried in vacuo to yield 1.865 g
(95%) of 17 as a white solid. Spectral data agreed with those reported
in the literature.46
Methyl 4-Oxooctadecanoate (28).47 Anhydrous THF (10 mL) was
added to CuI (1.26 g, 6.62 mmol) under Ar, and the mixture was chilled
to 0 °C. Tetradecylmagnesium bromide, 1 M in THF (6.60 mL, 6.60
mmol), was then added. The resulting gray-black mixture was stirred
at 0 °C for 20 min, then cooled to -78 °C, and methyl 4-chloro-4-
oxobutyrate (0.45 mL, 3.6 mmol) was added. The reaction mixture
was then warmed to 0 °C, stirred for 45 min, and quenched with H2O
(10 mL) and 1 M HCl (10 mL). Diethyl ether (30 mL) was then added
and the cloudy organic layer separated. The organic layer was filtered
through a 2.5-cm plug of Florisil to remove fine salts, then washed
with saturated NaHCO3 (2 × 10 mL) and saturated NaCl (2 × 10 mL)
solutions, and dried over MgSO4. The majority of the solvent was
removed under partial pressure, and the crude product was dried in
vacuo for 16 h. The resulting white solid was subsequently purified by
flash chromatography, eluting with an increasing fraction of 2-propanol
in CHCl3. Yield: 0.965 g of a white solid (94% from 1 equiv of
tetradecylmagnesium bromide). Spectral data were in agreement with
the literature.47
Methyl 4-Hydroxyoctadecanoate (19).46a Compound 28 (0.472 g,
1.51 mmol) was dissolved in methanol (50 mL), and the resulting
solution was chilled in an ice bath. NaBH4 (0.112 g, 1.50 mmol) was
added and the reaction mixture stirred at 0 °C for 30 min while H2 gas
evolved. H2O (10 mL) was then added, followed by dropwise addition
of 1 M HCl to bring the pH of the mixture to 3. After addition of
diethyl ether (2 × 20 mL), the organic layer was washed with 1 M
HCl (20 mL), H2O (2 × 25 mL), and saturated NaCl (2 × 15 mL),
and then dried briefly over MgSO4. Removal of the solvent under
reduced pressure, followed by drying in vacuo afforded 0.462 g (97%)
of pure 19 as a white solid. Spectral data were in agreement with those
reported in the literature.46a
materials as a function of pore size. We are also preparing
transition-metal salts of these styrene ether LLC monomers for
the formation of both nanoparticles and composite materials.
Experimental Section
General. All reagents and common solvents, including anhydrous
THF, CH2Cl2, and toluene, were purchased from the Aldrich Chemical
Co. and used as purchased unless otherwise noted. NaBH4 was
purchased from Alfa. HPLC grade methanol and CHCl3 were purchased
from Fisher Scientific. PCC/Al2O3 was prepared according to the
method of Cheng et al.31 4-Acetoxystyrene was hydrolyzed according
to the method of Corson et al.42 to give 4-vinylphenol as a white
crystalline solid that was stored at -20 °C until use. Unless otherwise
specified, organic extracts were dried over anhydrous MgSO4, and the
solvent removed with a rotary evaporator at aspirator pressure, followed
by drying under full vacuum on the Schlenk line (10-4 Torr). Column
chromatography (flash) was performed with 40 µm silica gel (J. T.
Baker). Reaction mixtures and chromatography fractions were moni-
tored with EM Science 250 µm silica gel F254 plates. 1H and 13C NMR
spectra were acquired at 500 and 125 MHz, respectively, using a Bruker
DRX-500 spectrometer. For NMR analysis, neutral organic compounds
were dissolved in CDCl3, and salts were dissolved in d4-methanol. FT-
IR spectra were obtained using a Perkin-Elmer 1616 series FT-IR
spectrometer. The samples were analyzed as neat compounds on NaCl
or Ge crystals, or as KBr mulls. Elemental analyses were performed at
Desert Analytics, Tuscon, AZ, and Quantitative Technologies Inc.,
Whitehouse, NJ. Optical textures were obtained using a Leica DMRXP
polarizing microscope equipped with a Wild MPS 48/52 automatic
camera assembly. Low-angle XRD profiles were obtained using an Inel
CPS 120 powder diffraction system employing Cu KR radiation.
Photopolymerizations were performed using a Cole-Parmer 9815 series
6 W UV (365 nm) lamp under N2 flush. Photopolymerization light
fluxes were measured using a Spectroline DRC-100X digital radiometer
equipped with a DIX-365 UV-A sensor.
Representative syntheses are presented below with a full listing of
characterization data (1H NMR, 13C NMR, FT-IR, and elemental
analysis43) for all new compounds. Compounds with chiral centers were
synthesized as racemic mixtures. Spectral data for all new compounds
and XRD peak listings for all LLC mixtures can be found in the
Supporting Information. Distinct signals for all nonequivalent carbons
in the alkyl backbones were not resolved in all cases due to the length
of the alkyl chains. Overlapping signals are indicated as a range with
the number of carbons represented.
Methyl 10-Hydroxydecanoate (23).44 Methanol (50 mL) was added
to 10-hydroxydecanoic acid (2.00 g, 10.6 mmol), followed by 10 drops
of concentrated sulfuric acid. The solution was heated at reflux for 16
h, cooled to ambient temperature, diluted with water (10 mL), and then
poured into ether (150 mL). The layers were separated, and the organic
layer was then washed with water (3 × 25 mL), saturated NaHCO3
(25 mL), and saturated NaCl (2 × 25 mL). After drying over MgSO4,
the solvent was removed under partial pressure, dry toluene was added
(20 mL), and the solvent was removed again. The final product was
dried in vacuo yielding 1.916 g (90%) of 23 as an oil which solidified
at 4 °C. Spectral data were consistent with those reported in the
literature.44
Methyl 10-(4-Vinylphenoxy)octadecanoate (34). A Schlenk flask
was charged with dry toluene (30 mL) under Ar and chilled to 0 °C.
Tributylphosphine (2.3 mL, 8.9 mmol) and 1,1′-(azodicarbonyl)-
dipiperdine (2.24 g, 8.89 mmol) were then added, and the resulting
solution stirred for 1 h at 0 °C while the solution’s bright yellow-orange
color faded away. Compound 17 (1.865 g, 5.94 mmol) and 4-vinylphe-
nol (0.800 g, 6.66 mmol) were combined and dissolved in anhydrous
toluene (15 mL) in a separate vessel and added dropwise to the reaction
mixture over a period of 15 min. A white solid formed during the
addition. The reaction mixture was stirred at 0 °C for 1 h and then
incubated without stirring at -18 °C for 24 h. After thin-layer
chromatography (CHCl3) indicated that the reaction had ceased, the
reaction mixture was diluted with pentane (200 mL) and chilled to 0
°C for 1 h. The mixture was subsequently filtered, and the solid washed
with more pentane (200 mL). The filtrate was then concentrated under
(42) Corson, B. B.; Heintzelman, W. J.; Schwartzman, L. H.; Tiefenthal,
H. E.; Lokken, R. J.; Nickels, J. E.; Atwood, G. R.; Pavlik, F. J. J. Org.
Chem. 1958, 23, 544.
(43) It is extremely difficult to completely remove residual water from
the amphiphilic monomer salts, the majority of which are extremely
hygroscopic. Consequently, the elemental analysis results for the final salts
typically do not agree within (0.5 wt % of the calculated values for the
pure salts. However, the elemental analysis results of the preceding parent
carboxylic acids of the final salts (prior to titration with aqueous base) do
agree to (0.5 wt % of expected values, and all other spectroscopic data
are consistent with the structures presented. Thus, the identities of the final
amphiphilic monomer salts are not in question. In addition, the elemental
percentages of the salts are consistent ((0.5%) with the expected values
when associated water molecules are factored in.
(45) Vinczer, P.; Baan, G.; Novak, L.; Szantay, C. Tetrahedron Lett.
1984, 25, 2701.
(46) (a) Tulloch, A. P. Org. Magn. Reson. 1978, 11, 109. (b) Tulloch,
A. P. Lipids 1976, 11, 228.
(44) Baldwin, J. E.; Adlington, R. M.; Ramcharitar, S. H. Tetrahedron
1992, 48, 2957.
(47) Jossang, A.; Melhaoui, A.; Bodo, B. Heterocycles 1996, 43, 755.

A New Family of Polymerizable Lyotropic Liquid Crystals
J. Am. Chem. Soc., Vol. 123, No. 3, 2001 371
partial pressure to yield a crude product. Purification by column
Tetraethylammonium 16-(4-Vinylphenoxy)octadecanoate (59).
Compound 42 (20 mg, 0.050 mmol) was dissolved in ethanol (1-2
mL). To the resulting solution was added a 20% solution of tetraethy-
lammonium hydroxide in H2O (35 µL, 0.050 mmol). After the majority
of the solvent was removed under partial pressure, the product was
dried in vacuo overnight to yield 0.027 g of a hygroscopic sticky solid
chromatography with CHCl3 elution afforded 1.93 g (84%) of pure 34
1
as a clear oil that solidified at -18 °C. H NMR (CDCl3): δ 7.32 (d,
2H), 6.83 (d, 2H), 6.65 (dd, 1H), 5.59 (dd, 1H), 5.11 (dd, 1H), 4.20
(quintet, 1H), 3.66 (s, 3H), 2.29 (t, 2H), 1.60 (m, 6H), 1.40 (m, 2H),
1.18 (m, 20H), 0.87 (t, 3H). 13C NMR (CDCl3): δ 174.3, 158.5, 136.2,
130.0, 127.3, 115.7, 111.3, 78.0, 51.4, 34.1, 33.9, 33.9, 31.8, 29.7, 29.6,
29.5, 29.3, 29.2, 29.1, 29.1, 25.3, 25.3, 24.9, 22.6, 14.1. FT-IR (cm-1):
2927 (s), 2854 (s), 1741 (s), 1628 (w), 1464 (m), 988 (s), 897 (s),
834 (m). Anal. Calcd for C27H44O3: C, 77.83; H, 10.64. Found: C,
77.62; H, 10.46.
1
(quantitative yield). H NMR (d4-methanol): δ 7.32 (d, 2H), 6.83 (d,
2H), 6.69 (dd, 1H), 5.60 (d, 1H), 5.07 (d, 1H), 4.21 (m, 1H), 3.29
(quartet, 8H), 2.15 (t, 2H), 1.62 (m, 6H), 1.28 (m, 34H), 0.945 (t, 3H).
13C NMR (d4-methanol): δ 181.0, 158.5, 136.2, 130.1, 127.0, 115.4,
110.1, 78.5, 51.7, 37.7, 33.1, 29.5, 29.4-29.2 (9 C signals), 26.3, 26.3,
24.9, 8.5, 6.2. FT-IR (cm-1): 2920 (s), 2850 (s), 1556 (s), 1507 (s),
1393 (s), 1242 (s), 999 (m), 894 (m). Anal. Calcd for 59 (C34H61O3N):
C, 76.78; H, 11.56; N, 2.63. Anal. Calcd for (59 + 4H2O)
(C34H69O7N): C, 67.62; H, 11.52; N, 2.32. Found: C, 66.98; H, 11.69;
N, 2.57.43
Preparation of LLC Phases and Photopolymerization. LLC
mixtures were prepared by first placing the appropriate amounts of the
LLC monomer salt and additives (see tables) in 40-mL centrifuge tubes
and mixing with a spatula by hand. The samples were then centrifuged
at 2600 rpm three times with the tubes inverted after each run and
allowed to equilibrate at ambient temperature (24 ( 1 °C) for a
minimum of 1 h before analysis. The LLC samples were prepared as
thin films on quartz plates for PLM analysis, on Al sample holders for
XRD analysis, or on Ge crystals for IR analysis. Photopolymerizations
were all carried out under light N2 flush over a period of 12 h at ambient
temperature with use of a 6 W UV (365 nm) lamp. The light flux at
the surface of the LLC samples during photolysis was 1800 µW/cm2.
Initial conversion of the LLC monomer mixtures to a glassy cross-
linked network typically occurs within the first hour of irradiation. The
degree of polymerization (i.e., double bond conversion) was determined
by monitoring the diminishment of the 988- and 896-cm-1 bands (olefin
C-H out-of-plane bending) relative to the 832-cm-1 band (para-
substituted aromatic C-H out-of-plane bending) by FT-IR spectrometry
(absorbance mode).
10-(4-Vinylphenoxy)octadecanoic Acid (44). A mixture of methanol/
H2O (4:1, 50 mL) and NaOH (0.500 g, 12.5 mmol) was added to 33
(1.10 g, 2.64 mmol). The resulting solution was heated at reflux for
4.5 h and then cooled to ambient temperature, at which time H2O (5
mL) and 1 M HCl (15 mL) were added to bring the pH of the mixture
to 2. The reaction mixture was extracted with 4:1 EtOAc/hexane (2 ×
100 mL), and the combined organic layers were washed with saturated
NaCl (2 × 50 mL). After drying over MgSO4, the organic layer was
concentrated under partial pressure to afford an oil. The product was
then dried in vacuo to a constant weight to give 0.745 g (71%) of pure
44 as a thick oil. 1H NMR (CDCl3): δ 10.90 (br s, 1H), 7.32 (d, 2H),
6.84 (d, 2H), 6.65 (dd, 1H), 5.59 (d, 1H), 5.11 (d, 1H), 4.16 (quintet,
1H), 2.35 (t, 2H), 1.64 (m, 6H), 1.28 (m, 22H), 0.94 (t, 3H). 13C NMR
(CDCl3): δ 179.5, 158.8, 136.5, 130.3, 127.6, 116.0, 111.5, 79.4, 34.1,
34.1, 33.6, 29.9, 29.9, 29.8, 29.8, 29.7, 29.7 29.5, 29.3, 26.8, 25.6,
24.9, 24.9, 9.79. FT-IR (cm-1): 2927 (s), 2854 (s), 1710 (s), 1628 (w),
1465 (m), 988 (s), 897 (s), 834 (m). Anal. Calcd for C26H42O3: C,
77.56; H, 10.51. Found: C, 77.46; H, 10.63.
Sodium 10-(4-Vinylphenoxy)octadecanoate (7). Compound 44
(0.361 g, 0.897 mmol) was dissolved in ethanol (5 mL) and then
neutralized with NaOH (37 mg, 0.9 mmol) in H2O (2 mL). The solvents
were removed under partial pressure, and the product was dried in vacuo
for 16 h to afford 0.377 g of 7 (99%) as a sticky, flaky white solid. 1H
NMR (d4-methanol): δ 7.30 (d, 2H), 6.81 (d, 2H), 6.62 (dd, 1H), 5.58
(d, 1H), 5.04 (d, 1H), 4.25 (quintet, 1H), 2.13 (t, 2H), 1.58 (m, 6H),
1.28 (m, 22H), 0.864 (t, 3H). 13C NMR (d4-methanol): δ 183.3, 160.1,
137.8, 131.7, 128.6, 117.0, 111.6, 79.03, 39.47, 35.23, 35.18, 35.15,
33.15, 30.99, 30.95, 30.81, 30.76, 30.73, 30.49, 27.95, 26.55, 26.47,
23.86, 14.61. FT-IR (cm-1): 2917 (s), 2847 (s), 1572 (s), 1508 (s),
1422 (m), 1243 (m), 987 (s), 896 (s), 833 (m). Anal. Calcd for C26H41O3-
Na: C, 73.55; H, 9.73; Na, 5.41. Anal. Calcd for (7 + H2O) (C26H43O4-
Na): C, 70.55; H, 9.79; Na, 5.19. Found: C, 71.41; H, 9.90; Na, 5.60.43
Tetramethylammonium 10-(4-Vinylphenoxy)octadecanoate (57).
Compound 44 (85 mg, 0.21 mmol) was dissolved in ethanol (5 mL).
To the resulting solution was added a 25% solution of bis(tetramethy-
lammonium)carbonate in H2O (85 µL, 0.11 mmol). The solvent was
removed under partial pressure, and the product dried in vacuo overnight
Acknowledgment. Partial financial support for this work
was provided by the National Science Foundation through a
CAREER award to D.L.G. (DMR-9625433). Additional finan-
cial support from the Office of Naval Research (N00014-97-
1-0207), the Donors of the ACS Petroleum Research Fund
(33632-AC5,7), and a Research Fellowship from the Alfred P.
Sloan Foundation to D.L.G. are also gratefully acknowledged.
We also thank Dr. Weiqiang Gu for his assistance in the final
revision of this manuscript.
Supporting Information Available: Full experimental
details and characterization data for all new compounds
synthesized in this study; XRD data for the LLC phases of
monomers 2-11 and 55-59 in neat form and as mixtures with
water and DVB (before and after cross-linking); representative
plots showing the small changes in the XRD peaks of the
unpolymerized and polymerized HII phases of 7 with increasing
temperature (PDF). This material is available free of charge via
the Internet at http://pubs.acs.org.
1
to give 0.103 g of an hygroscopic sticky solid (quantitative yield). H
NMR (d4-methanol): δ 7.29 (d, 2H), 6.80 (d, 2H), 6.65 (dd, 1H), 5.56
(d, 1H), 5.04 (d, 1H), 4.23 (m, 1H), 3.15 (s, 12H), 2.11 (t, 2H), 1.54
(m, 6H), 1.27 (m, 22H), 0.85 (t, 3H). 13C NMR (d4-methanol): δ 183.0,
160.1, 137.8, 131.7, 128.6, 117.0, 111.7, 79.1, 56.0, 39.6, 35.2, 35.2,
33.2, 31.0, 30.9, 30.7, 30.7, 30.5, 30.5, 28.0, 26.6, 26.5, 23.9, 23.9,
14.6. FT-IR (cm-1): 2919 (s), 2837 (s), 1572 (s), 1248 (s), 985 (m),
897 (m), 832 (s). Anal. Calcd for 57 (C30H53O3N): C, 75.74; H, 11.23;
N, 2.94. Anal. Calcd for (57 + 2H2O) (C30H57O5N): C, 70.41; H, 11.23;
N, 2.74. Found: C, 70.06; H, 11.68; N, 3.29.43
JA002462I