vesicles. The morphology development was governed by the PEO block length
[41]. As a function of the temperature, the micelles reversibly transfer between the
two immiscible fluids, traveling in and out of the water and IL phases. This
temperature-driven micelle partitioning creates versatile micelle shuttles and
nanocarriers that are useful in “round-trip” delivery systems, biphase catalysis,
and separation technology [42].
In the third strategy, heterophase polymerization reactions such as suspension
polymerizations and micro- and mini-emulsion polymerizations produce stable
dispersions of monodisperse PIL particles. Typically, their average diameters
vary from nano- to micrometer dimensions [43–46]. Such processes also enable
the preparation of gel-like PIL particles [47, 48] and of solvent-reversible poration
in copolymer ionic liquids [49]. Moreover, in aqueous precipitation polymerization,
highly ordered PIL nanoparticles with average diameter of 20–40 nm are obtained.
Their tunable multilamellar and unilamellar vesicular inner structures resemble
those of liposomes [50, 51]. NanoPILs, mesoporous PILs, and PIL nanoparticles are
tailored for applications in biocatalysis and sensing [45–49, 52]. The incorporation
of three-dimensionally ordered macropores and nanoparticles in nanoPILs is the
key to a new generation of smart materials and functional films that are useful as
tunable photonic crystals, anion-directed molecular gating systems, electrooptical
switches, and functional surfaces with tunable wettability [53]. Most PILs are
highly effective phase-transfer media and dispersing agents for nanoparticles such
as carbon nanotubes (CNT) and metal nanoparticles, enabling their transport from
aqueous into nonaqueous phases [54–56]. Novel PIL/CNT nanohybrid materials
represent electroactive nanomaterials, known as “bucky plastics” [57, 58].
3 Nanostructured Hyperbranched PILs
with Micelle-Like Topologies
Whereas numerous reports describe linear nanoPILs, much less is known regarding
dendritic and hyperbranched nanoPILs with molecular architectures resembling
micelles. Unlike micellar ILs, tree-like branched nanoPILs with core–shell and
onion-like topologies are much less sensitive to high shear forces and changes in pH
and temperature. For the first time, the groups of Aida and Percec succeeded in
preparing dendritic polyelectrolytes that self-organized [59] and formed cylindrical
nanoobjects [60]. In order to qualify for PIL applications, however, low viscosity and
low glass transition temperatures are required. Moreover, in view of scale-up, the
one-pot formation of hyperbranched PILs is highly advantageous with respect to
dendrimer-based nanoPILs, produced in tedious multistep syntheses. As commercially available highly branched liquid polymers, polyethyleneimines, containing
quarternary ammonium cations, are attractive intermediates for PIL formation. For
example, Domb and coworkers derived amphiphilic nanoPILs from commercially
available polyethyleneimine, which was crosslinked with dibromopentane,
Nanostructured Polymeric Ionic Liquids
435
[41]. As a function of the temperature, the micelles reversibly transfer between the
two immiscible fluids, traveling in and out of the water and IL phases. This
temperature-driven micelle partitioning creates versatile micelle shuttles and
nanocarriers that are useful in “round-trip” delivery systems, biphase catalysis,
and separation technology [42].
In the third strategy, heterophase polymerization reactions such as suspension
polymerizations and micro- and mini-emulsion polymerizations produce stable
dispersions of monodisperse PIL particles. Typically, their average diameters
vary from nano- to micrometer dimensions [43–46]. Such processes also enable
the preparation of gel-like PIL particles [47, 48] and of solvent-reversible poration
in copolymer ionic liquids [49]. Moreover, in aqueous precipitation polymerization,
highly ordered PIL nanoparticles with average diameter of 20–40 nm are obtained.
Their tunable multilamellar and unilamellar vesicular inner structures resemble
those of liposomes [50, 51]. NanoPILs, mesoporous PILs, and PIL nanoparticles are
tailored for applications in biocatalysis and sensing [45–49, 52]. The incorporation
of three-dimensionally ordered macropores and nanoparticles in nanoPILs is the
key to a new generation of smart materials and functional films that are useful as
tunable photonic crystals, anion-directed molecular gating systems, electrooptical
switches, and functional surfaces with tunable wettability [53]. Most PILs are
highly effective phase-transfer media and dispersing agents for nanoparticles such
as carbon nanotubes (CNT) and metal nanoparticles, enabling their transport from
aqueous into nonaqueous phases [54–56]. Novel PIL/CNT nanohybrid materials
represent electroactive nanomaterials, known as “bucky plastics” [57, 58].
3 Nanostructured Hyperbranched PILs
with Micelle-Like Topologies
Whereas numerous reports describe linear nanoPILs, much less is known regarding
dendritic and hyperbranched nanoPILs with molecular architectures resembling
micelles. Unlike micellar ILs, tree-like branched nanoPILs with core–shell and
onion-like topologies are much less sensitive to high shear forces and changes in pH
and temperature. For the first time, the groups of Aida and Percec succeeded in
preparing dendritic polyelectrolytes that self-organized [59] and formed cylindrical
nanoobjects [60]. In order to qualify for PIL applications, however, low viscosity and
low glass transition temperatures are required. Moreover, in view of scale-up, the
one-pot formation of hyperbranched PILs is highly advantageous with respect to
dendrimer-based nanoPILs, produced in tedious multistep syntheses. As commercially available highly branched liquid polymers, polyethyleneimines, containing
quarternary ammonium cations, are attractive intermediates for PIL formation. For
example, Domb and coworkers derived amphiphilic nanoPILs from commercially
available polyethyleneimine, which was crosslinked with dibromopentane,
Nanostructured Polymeric Ionic Liquids
435