Co-assembled conductive hydrogel of N-fluorenylmethoxycarbonyl phenylalanine with polyaniline.

Abstract

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.