Diphenylpolyacetylenes bearing long alkyl silyl side chains: Lyotropic liquid-crystalline and polarized absorption and fluorescence properties

Recently, considerable synthetic and processing efforts directed towards polarized fluorescence materials such as liquid crystalline (LC) conjugated polymer have been intensively performed in the field of liquid-crystalline display devices. To accomplish the uniaxial molecular alignment in the polymer film, it should be one of the most promising methods to add LC nature to individual polymer chains and then apply external force such as shear stress or an electric or magnetic field to the LC state. In a previous paper, we reported syntheses of several unique poly(diphenylacetylene) derivatives bearing long alkyl side chains linked by silylene moiety, polymers 1 and 2 shown in Scheme 1. Herein we found that these polymers exist as L C in concentrated aromatic organic solvents such as toluene, and show strongly polarized absorption and fluorescence in the sheared films. The main axes of absorption and fluorescence from the main chain were in perpendicular to the shearing direction rather than in parallel.