Poly(N-alkyl pyridinium salt) was synthesized as an ionic polymer phase for HPLC packing material in which the separation mode can be easily tuned by changing the alkyl side chains through quaternization reactions with various alkyl halides. The prepared ionic polymer phase with methyl pyridinium side chains showed good separations of hydrophilic biomolecules in hydrophilic-interaction liquid chromatographic mode, which is different from that with octadecyl pyridinium side chains showing better performance in reversed phase HPLC mode.