AROMATIC POLYMER HAVING BOTH AZOBENZENE AND AZOMETHINE UNITS IN THE MAIN CHAIN AS AN EFFICIENT PHOTO-RESPONSIVE MATERIAL

Abstract

Azobenzene and aromatic azomethine groups acting as versatile photoreversible optically switchable scaffolds attract much interest as efficient building blocks for the construction of light-responsive materials. The pronounced interest in light-sensitive polymers originates from their unique ability to become anisotropic after irradiation by polarized light. Despite the significant progress that has been made on the synthesis of either polyazobenzenes or polyazomethines, numerous challenges remain, and they have become the catalyst for the ongoing research. The polymer having both azobenzene and azomethine groups are fundamentally less developed. In this work, a strategy to the synthesis of the light-responsive polymer with azobenzene and azomethine units in the backbone is proposed. The polymer is prepared by condensation polymerization of octafluorobiphenylene-based bis-hydroxybenzaldehyde with aromatic meta-linked octafluorobiphenylene-based diamine. The structure of the polymer is characterized by Fourier transform infrared spectroscopy. The synthesized polymer can be solution-cast into flexible solid films with a tensile strength of 25 MPa. Furthermore, the polymer displays elevated glass transition temperatures (Tg), reaching 235 °C, and demonstrates an admirable thermal stability, retaining resilience at temperatures up to 390 °C. The polymer film underwent photoisomerization and exhibited changes in light-induced birefringence when exposed to 365 nm UV light and both polarized and unpolarized blue (405 nm) and green (532 nm) light. The ability to record optical information using polymer films in the form of diffraction gratings is demonstrated.