Synthesis and solid-state properties of thermotropic liquid crystalline polypeptide bearing imidazolium and p-tolyl groups

•We prepared thermotropic liquid crystalline polypeptides bearing imidazolium and p-tolyl groups.•We examined the solid-state structures and thermal properties of the resulting polypeptides.•Increasing p-tolyl contents give rise to more stable liquid crystalline phase and higher glass transition temperatures.

Polypeptides bearing imidazolium and p-tolyl groups have been synthesized by click chemistry between poly(γ-3-azidopropyl-l-glutamate) (PAPLG) and 3-butyl-1-propargyl imidazolium bromide (BPIB) and 1-methyl-4-prop-2-ynyloxybenzene (MPB). The FTIR results revealed α-helical conformation of all resulting polypeptides in the solid-state. POM and WAXS study revealed that polypeptides with high p-tolyl contents (molar percentage ⩾54%) possessed nematic liquid crystalline phases and hexagonal packing in the solid-state. DSC analysis revealed the solid to liquid crystalline transitions in the temperature range of 35–42 °C.

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