Interfacial polarization and electrorheological effect of homo-poly(ionic liquid) and poly(ionic liquid)-hexyl methacrylate copolymer microsphere particles

Homo-poly(ionic liquid) (HomoPIL) microsphere particles of poly[2-(methacryloyloxy)ethyltrimethylammonium][bis(trifluoromethanesulfonyl)imide] (P[MTMA][TFSI]) and poly[2-(methacryloyloxy)ethyltrimethylammonium][hexafluorophosphate] (P[MTMA][PF₆]), as well as their corresponding copolymer microsphere particles obtained through copolymerization with hexyl methacrylate (HMA), were synthesized as electrorheological (ER) materials. The morphology and structure of these synthesized particles were characterized using scanning electron microscopy (SEM), ¹H nuclear magnetic resonance spectroscopy (¹H NMR), Fourier-transform infrared spectroscopy (FT-IR), and small-angle X-ray scattering spectra (SAXS). Electrorheological measurements were conducted for these polyelectrolyte-based suspensions at room temperature, revealing that the HMA composition has a different effect on the ER effect of the two poly(ionic liquid)s. Differential scanning calorimetry (DSC) and temperature-modulated dielectric analysis (TMDA) were employed to investigate the effect of HMA composition on the glass transition temperature and interfacial polarization of these polyelectrolytes, suggesting that the incorporation of HMA affect the ER effect of PILs via changing the density of charge carriers and the counterion mobility. This study presents a potential approach for enhancing the electrorheological properties of poly(ionic liquid)s.