as poly(1-vinyl-3-butylimidazolium) bromide afforded polyelectrolyte membranes
with enhanced ionic conductivity [76]. As electrode materials for supercapacitors,
graphene in conjunction with poly(1-vinyl-3-ethylimidazolium) bis(trifluoromethylsulfonyl)amide accounted for substantial improvement in capacity [77]. As
highly selective gas sensors, multilayer carbon composite films were obtained by
reducing graphite oxide dissolved in ILs, followed by electrostatic layer-by-layer
assembly [78]. In an elegant one-pot synthesis, fluorescent carbon nanoribbons,
nanoparticles, and graphene were prepared by IL-mediated electrochemical
exfoliation of graphite [79]. Novel IL/graphene lubricants exploit interfacial
nanostructure formation, owing to thin film formation resulting from self-assembly
of graphene. This contributes to a reduction in frictional forces, thus enhancing
tribological performance [80].
Going well beyond the noncovalent graphene/PIL interactions and the assembly
of PIL at the graphene interface, several successful approaches have been reported
on the covalent attachment of IL and PIL to graphene. Yang and coworkers reported
on the immobilization of 1-(3-aminopropyl)-3-methylimidazolium bromide on
graphite oxide [81]. In an alternative approach, graphite oxide was amidated
using 1-(3-aminopropyl)imidazole, followed by alkylation of the imidazole with
1-bromobutane [82]. Using 1,3-dipolar cycloaddition reactions, Quintana
et al. decorated graphene sheets with ammonium chloride functions [83] and
protonated polyamidoamine dendrons [84], both of which were linked to the
graphene surface via pyrrolidine rings. In a mild, one-step electrochemical process,
IL-functionalized graphene nanosheets were produced from graphite [85].
Several “grafting-from” and “grafting-to” strategies were introduced for
covalent attachment of polymer chains to graphene, aiming at the formation of
novel molecular carbon/polymer composites and graphene brushes. Progress was
reviewed by Salavagione et al. [86]. In grafting-from processes, a variety of
initiators and transfer agents were covalently attached to graphene. For example,
graphite oxide was reacted with α-bromoisobutyryl bromide in order to prepare
macro-initiators for grafting by means of atom transfer radical polymerization,
ATRP [87, 88]. In the grafting-from process, by means of reversible addition
fragmentation chain transfer polymerizations (RAFT), various dithioesters,
trithiocarbonates, dithiocarbamates, and xanthogenates were covalently attached
to functionalized graphene and graphite oxide and used as macrochain transfer
agents [89–91]. For example, in a multistep process, the carboxylic acid groups of
graphite oxide were transformed into dithiobenzoates [92]. In a recent advance, the
self-initiated styrene homo- and copolymerization was initiated by organophilic
stearylamine-modified graphite oxide. In this process, efficient graphene grafting
was achieved without requiring either the addition or the incorporation of initiators,
transfer agents, or polymerizable groups. According to an on-line electron
paramagnetic resonance (EPR) monitoring of this reaction, both the addition of
polymer radicals to graphene and hydrogen transfer from graphene play important
roles [93]. Little is known with respect to grafting PILs onto graphene and CNTs.
CNTs with partially quaternized, covalently attached poly(4-vinylpyridine) brushes
represent an example of PIL-functionalized nanostructured carbon materials [94].
Nanostructured Polymeric Ionic Liquids
439
with enhanced ionic conductivity [76]. As electrode materials for supercapacitors,
graphene in conjunction with poly(1-vinyl-3-ethylimidazolium) bis(trifluoromethylsulfonyl)amide accounted for substantial improvement in capacity [77]. As
highly selective gas sensors, multilayer carbon composite films were obtained by
reducing graphite oxide dissolved in ILs, followed by electrostatic layer-by-layer
assembly [78]. In an elegant one-pot synthesis, fluorescent carbon nanoribbons,
nanoparticles, and graphene were prepared by IL-mediated electrochemical
exfoliation of graphite [79]. Novel IL/graphene lubricants exploit interfacial
nanostructure formation, owing to thin film formation resulting from self-assembly
of graphene. This contributes to a reduction in frictional forces, thus enhancing
tribological performance [80].
Going well beyond the noncovalent graphene/PIL interactions and the assembly
of PIL at the graphene interface, several successful approaches have been reported
on the covalent attachment of IL and PIL to graphene. Yang and coworkers reported
on the immobilization of 1-(3-aminopropyl)-3-methylimidazolium bromide on
graphite oxide [81]. In an alternative approach, graphite oxide was amidated
using 1-(3-aminopropyl)imidazole, followed by alkylation of the imidazole with
1-bromobutane [82]. Using 1,3-dipolar cycloaddition reactions, Quintana
et al. decorated graphene sheets with ammonium chloride functions [83] and
protonated polyamidoamine dendrons [84], both of which were linked to the
graphene surface via pyrrolidine rings. In a mild, one-step electrochemical process,
IL-functionalized graphene nanosheets were produced from graphite [85].
Several “grafting-from” and “grafting-to” strategies were introduced for
covalent attachment of polymer chains to graphene, aiming at the formation of
novel molecular carbon/polymer composites and graphene brushes. Progress was
reviewed by Salavagione et al. [86]. In grafting-from processes, a variety of
initiators and transfer agents were covalently attached to graphene. For example,
graphite oxide was reacted with α-bromoisobutyryl bromide in order to prepare
macro-initiators for grafting by means of atom transfer radical polymerization,
ATRP [87, 88]. In the grafting-from process, by means of reversible addition
fragmentation chain transfer polymerizations (RAFT), various dithioesters,
trithiocarbonates, dithiocarbamates, and xanthogenates were covalently attached
to functionalized graphene and graphite oxide and used as macrochain transfer
agents [89–91]. For example, in a multistep process, the carboxylic acid groups of
graphite oxide were transformed into dithiobenzoates [92]. In a recent advance, the
self-initiated styrene homo- and copolymerization was initiated by organophilic
stearylamine-modified graphite oxide. In this process, efficient graphene grafting
was achieved without requiring either the addition or the incorporation of initiators,
transfer agents, or polymerizable groups. According to an on-line electron
paramagnetic resonance (EPR) monitoring of this reaction, both the addition of
polymer radicals to graphene and hydrogen transfer from graphene play important
roles [93]. Little is known with respect to grafting PILs onto graphene and CNTs.
CNTs with partially quaternized, covalently attached poly(4-vinylpyridine) brushes
represent an example of PIL-functionalized nanostructured carbon materials [94].
Nanostructured Polymeric Ionic Liquids
439