Enhanced redox property of polymer blends containing liquid crystalline molecules and their application in electrochemical sensing

A series of thermoplastic polyester elastomer (TPEE) derivatives based on recycled polyethylene terephthalate (r-PET) and poly(tetramethylene glycol) together with differing amounts (n%, n = 0, 1, 3, and 5) of 1,6-hexanediamine (HDA) were prepared. Blending of the copolymer with a rod-like liquid crystal (4-cyano-3-fluorophenyl 4-ethylbenzoate (4CFE)), named TPEEn%-4CFE, was studied. Among them, the TPEE3%-4CFE mixture featured optimal blending, with liquid crystals well-connected with the HDA moieties in the TPEE framework through hydrogen-bonding interaction, according to X-ray and Fourier-transform infrared spectroscopy analyses. A packing diagram is proposed to illustrate the unique performance of TPEE3%-4CFE, attributed to the enhancement of π–π interactions. The polarized mesophase and morphology indicated favorable dispersion of liquid crystals in the TPEE matrix in TPEE3%-4CFE, which was applied successfully in electrochemical sensing for ascorbic acid for the first time. The TPEE3%-4CFE-modified carbon paste electrode sensor is a rapid-response sensor with high sensitivity of approximately 11.30 μA mM⁻¹, a wide linear dynamic range of 0.181.26 μM, and a limit of detection of 0.4 mM–1.6 mM.