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sions. In addition, the hydrophilic polar headgroups of the LLC mesogens
are localized exclusively and densely in the walls of LLC cavities via the am-
phiphilic self-assembly process. This arrangement can lead to electrostatic,
hydrophobic, electrophilic, and/or nucleophilic interactions that can cause
a change in free energy activation for the overall process and affect reaction
rate. This is similar to what is believed to occur during catalysis in micelle
systems [98-100]. The open domains in LLC phases may impose dimensional
constraints that allow reactants with certain sizes or shapes to enter more
easily than others, or favor the formation of certain transition state configu-
rations over others, to give rise to enhanced reaction selectivity. These effects
would be similar to how inorganic zeolites and molecular sieves operate as
selective heterogeneous catalysts [101]. If the hydrophilic headgroups in the
LLC pore domains were made to be catalytically active, the resulting LLC
phases could afford a much higher local density of catalytic groups in the
pores for reactions to occur than is typically possible in normal solution or
heterogeneous catalysis environments.
The past 10-15 years have seen major advances in the development and
realization of LLC materials for catalytic applications. These advances range
from the use of non-catalytically functionalized LLC phases as a means of
accelerating reactions via confinement, to the design of polymerized LLC ma-
terials containing discrete catalytic groups that act like organic analogues to
catalytic molecular sieves.
4.1
LLCPhasesasReactionMedia
The earliest examples demonstrating the promise of LLC materials for accel-
erating chemical reactions involved the use of LLC phases of commercially
available ionic or non-charged surfactants in water as nanoscale reaction
media. In these systems, the surfactants and resulting LLC phases were not
functionalized with any catalytic or reactive groups. All the reactants and
catalytic entities were from external sources and solubilized in the LLC do-
mains during reaction. Consequently, the rate acceleration effects observed in
these systems can be attributed to the same types of confinement, solubiliza-
tion, and electronic interactions found in micellar catalysis systems [98-100].
4.1.1
Catalysis of Small Molecule Transformations
One of the first examples of catalysis inside non-functionalized LLC phases
involved the type I LLC phases of the cationic surfactant, cetyl trimethylam-
monium bromide (CTAB), and its longer analogs [102]. These LLC phases
were able to accelerate the deprotonation of (
p
-nitrophenoxy)propiophenone
by
n
-decyl-N(O
-
)-Bz acting as a base. The rate of this base-catalyzed reac-
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