Synthesis and characterization of "comb-like" poly(ionic liquid-co-styrene): expected applications in graphene dispersion and CO sub(2) separation

Poly(ionic liquid)s (PILs) with well-defined architectures have shown significant potential in various fields, but establishing an easy method for their synthesis remains a challenge. Herein, comb-like copolymers with polystyrene and PIL as backbones and side chains, respectively, were prepared by directly polymerizing ionic liquid monomer by atom transfer radical polymerization using poly(styrene-co-4-vinylbenzyl chloride) as macroinitiator. NMR, GPC, and FTIR were used to characterize the molecular weights and compositions of macroinitiators and resultant copolymers. Results demonstrated successful synthesis, and also indicated that graft density and side chain length of the comb-like copolymers can be readily controlled by tuning macroinitiator composition and polymerization time. DSC and EIS measurements were further performed to investigate the thermal and electrochemical properties of comb-like copolymers with various architectures. Both glass transition temperature and impedance were found to highly depend on structure, particularly on the graft density of side chains. Furthermore, these comb-like copolymers were used both as stabilizer to disperse reduced graphene oxide (RGO) nanoplatelets in organic solvent and as an additive for N sub(2)/CO sub(2) separation membranes. As compared to neat PIL, a highly stable suspension of RGO in propylene carbonate and a composite membrane with enhanced N sub(2)/CO sub(2) selectivity were obtained in the presence of comb-like copolymers. Given the many advantages of diverse compositions, multiple groups, and tunable structure of PILs, the comb-like copolymers show great promising in stabilizing carbon materials and membrane separation.