Co-Assembled Conductive Hydrogel of N‑Fluorenylmethoxycarbonyl Phenylalanine with Polyaniline

A metastable coassembled hydrogel of N-Fluorenylmethoxycarbonyl (Fmoc) phenylalanine (FP) with aniline (FP–ANI), upon polymerization, produces a stable green-colored coassembled FP–polyaniline (FP–PANI) hydrogel. The coassembly is produced by supramolecular interactions between FP and ANI/PANI. WAXS spectra suggest that structures of FP powder, FP–ANI, and FP–PANI xerogels are different from each other. The FP–ANI gel exhibits a mixture of doughnut and fiber morphology, but the FP–PANI gel exhibits a nanotubular morphology. UV–vis spectroscopy suggests that the doped state of PANI and the fluorescence property of FP completely vanish in the FP–PANI gel. The storage and loss modulii (G′ and G″) of the FP–PANI gel are higher than those of the FP–ANI gel. The FP–ANI gel breaks at a lower oscillator stress (57 Pa) than the FP–PANI gel (93 Pa), which exhibits a good strain recovery demonstrating excellent viscoelastic properties. The FP–PANI gel also exhibits a dc conductivity (1.2 × 10^–2 S·cm^–1) that is seven orders higher than that of the FP–ANI gel because of the doped nature of PANI. The current–voltage (I–V) characteristic curve of FP–PANI xerogel resembles the behavior of a semiconductor–metal junction, and upon white light irradiation, it exhibits a reversible on–off cycle with a constant photocurrent value of 0.1 mA. The Nyquist plot obtained from impedance measurements of the FP–PANI xerogel is different from that obtained for the FP–ANI xerogel, and it exhibits almost a semicircle, indicating the existence of both resistive and capacitive features connected in parallel mode.