Synthesis and Characterization of Photorefractive Polymers Containing Transition Metal Complexes as Photosensitizer

Abstract

This paper reports detailed synthesis and characterization of a hybridized polymer system which combines the ionic transition metal complexes and a conjugated polymer backbone bearing NLO chromophores to manifest a large photorefractive (PR) effect. In this system, the conjugated polymer backbone was chosen to play the dual role of a transporting channel for the charge carriers and a macroligand to chelate with the transition metal complex. Ru(II)−tri(bispyridyl) complexes were chosen as the photocharge generator by utilizing their metal-to-ligand charge transfer properties. The Heck coupling reaction was applied to synthesize these multifunctional polymers. A large net optical gain (>200 cm-1) at a zero electric field was observed on poled samples. The synthetic approach is versatile and was extended to the synthesis of PR polymers containing Os complexes. The resulting polymer showed photorefractivity at a wavelength in the near IR region (780 nm). This approach also offers the opportunity to fine-tune the electronic properties of polymers through modification of the polymer structures. Model reactions were studied to elucidate the structural defects caused by the side reactions in the Heck reaction. The effects of these defects on the PR performance of these polymers were evaluated. It was demonstrated that eliminating these defects could enhance the photorefractive response time.