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Poly(ionic liquid) Nanolayers
Scott M. Husson, Department of Chemical and Biomolecular Engineering, Clemson University
Polymerized ionic liquids have excellent thermal resistance, high CO2 sorption capacities at low pressure,
fast reversible adsorption/desorption, and exceptional selectivity for CO2 over permanent gases. These
properties make pILs outstanding candidates as membrane separation layers for selective CO2 recovery
from gas mixtures that are generated by combustion of fossil fuels.
Our approach uses surface-initiated atom transfer radical polymerization to produce highly uniform pIL
nanolayers with controllable chain densities and independently controllable thicknesses. We have
exploited this flexibility and control to systematically study how nanolayer structure, in addition to
chemistry, affects CO2 sorption. One result is shown below that illustrates how grafting time is used to
control nanolayer thickness at constant chain density. The pIL nanolayers, when grafted from a solid
support, transform them into a CO2 selective sorbent. We also have measured CO2 adsorption isotherms
for grafted pILs that vary in layer thickness and pIL anion (BF4-, CH3SO3-, CF3SO3-).
0.08
40
CO2 with BF4
h
30
-
CO2 with CF3SO3
0.06
-
CO2 with CH3SO3
25
q (mmol/g)
pIL thickness (nm)
35
20
15
10
N2 with BF4
-
-
0.04
0.02
5
0
d
0.00
0
5
10
15
20
25
polymerization time (h)
Growth of pIL nanolayers demonstrating
that layer thickness can be controlled
independently of chain density
0.0
0.4
0.8
1.2
1.6
2.0
2.4
pressure (bar)
Membrane support coated with pIL nanolayers
adsorb CO2 with high selectively over N2