Photo-response orientation behaviors of polyethylene imine backbone structures with azobenzene side chains

Abstract

Polyethylene imines (PEIs) with azobenzene side groups, PEI6M and IP-DAz, were synthesized and the effects of the substitution degree of the PEI backbone structures on the photoresponse properties and the orientation behaviors were investigated. The phase transition temperatures are closely related to thermal stability in orientational order. IP-DAz showed only the smectic phase in a much broader range between 53 °C and 170 °C and the thermal stability was significantly improved compared with PEI6M. Reversible changes in absorption spectra relating to photoisomerization behavior for both polymers were observed by UV and visible light irradiation. Uniaxial orientation for the selective direction was induced by irradiation by linearly polarized light and the anisotropic properties were investigated by measurements of the order parameter and birefringence. Rapid photoresponses for molecular orientations were demonstrated for both polymers. Although the order parameter of IP-DAz was lower than that of PEI6M, the birefringence of IP-DAz for in-plane orientation was as high as for PEI6M and is related to the stable orientational order. © 2013 Society of Chemical Industry