Applications of wittig reactions in dibenzo 18-crown-6-ether substituted phenylenevinylene oligomer-synthesis, photo luminescent, and dielectric properties

摘要

Novel phenylenevinylene oligomer substituted dibenzo 18-crown-6 ether ring (DB-OPV) was synthesized using dibenzo 18-crown-6 with terephthaldicarboxaldehyde via Wittig reaction. Formation of the oligomer was confirmed by spectral (FT-IR, 1H and13C-NMR), gel-permeation chromatography and elemental analysis. The morphology of the oligomer film of one-dimensional and three-dimensional architectures was observed using atomic force microscopy. The oligomer showed excellent photoluminescence with bluish green emission maxima at shorter wavelengths of 505 nm. Stability of the oligomer was analyzed using UV spectroscopy with varying time and temperature. The dielectric properties such as dielectric constant and loss factor for the oligomer have also been studied with respect to change of frequency (50 Hz-5 MHz) and temperature (30-60°C). The value of dielectric constant decreased with increasing frequency, which indicates that the major contribution to the polarization comes from orientation polarization. The value of dielectric constant increased with increasing temperature which is due to greater freedom of movement of the dipole molecular chains within the oligomer at high temperature