Comparison between polymerized ionic liquids synthesized using chain-growth and step-growth mechanisms used as stationary phase in gas chromatography

• Imidazolium based polymeric ionic liquid phases were manufactured.
• Polymers obtained via chain- and step-growth mechanisms were prepared.
• Step-growth polymer showed excellent thermal stability as stationary phase.
• Optimal plate heights down to 0.4 mm were obtained on 0.25 mm columns.
• The high polarity and broad applicability of the phases was demonstrated.

In this study the merits of polymerized imidazolium based ionic liquid (PIL) stationary phases obtained via condensation and free radical polymerizations are compared as stationary phases in gas chromatography (GC). Poly(1-vinyl-3-butyl-imidazolium – bis(trifluoromethane)sulfonamide) (poly(ViC4Im+ NTf2−)) was obtained via a chain-growth mechanism while poly(propylimidazolium-NTf2) (poly(C3Im+ NTf2−)) was synthesized via a step-growth polymerization. The thermal stability of both polymers was assessed using thermal gravimetric analysis and compared with bleeding profiles obtained from the statically coated GC columns (30 m × 0.25 mm × 0.25 μm). The performance was compared to what could be obtained on commercially available 1,5-di(2,3-dimethylimidazolium)pentane2+ 2NTf2− (SLB-IL111) ionic liquid based columns. It was observed that the step-growth polymer was more thermally stable, up to 325 °C, while the chain-growth polymer showed initial degradation at 250 °C. Both polymers allowed reaching minimal plate heights of 0.400–0.500 mm for retained solutes such as benzaldehyde, acetophenone, 1-methylnaphthalene and aniline. Assessment of the McReynolds constants illustrated that the polarity of the step-growth polymer was similar to the SLB-IL111 column, while displaying improved column stability. The PIL phases and particularly the so far little studied condensation based polymer shows particular retention and satisfactory column performance for polar moieties such as esters, amine and carbonyl functionalities.