Liquid crystalline and photocrosslinkable poly(4,4′-stilbeneoxy) alkylarylphosphates

Three series of liquid crystalline and photocrosslinkable poly(4,4'-stilbeneoxy) alkylarylphosphates were synthesized from various 4,4'-bis(m-hydroxyalkyloxy)stilbenes (m = 2, 4, 6, 8, 10) and arylphosphorodichloridates in chloroform by solution polycondensation method. Polarized optical microscope (POM) and differential scanning calorimetry (DSC) observations revealed that polymers containing less than four methylene spacer groups did not exhibit liquid crystalline (LC) texture, possibly due to smaller microdomain and restricted movement of the mesogen. In contrast, polymers containing more than four methylene spacer group established LC texture, which has been attributed to the larger monodomain and free movement of mesogens. Thermogravimetric analysis (TGA) data indicated that thermal stability and char yield decreased with increasing flexible methylene spacer groups, increased significantly for biphenyloxy and 1-naphthyloxy containing polymers than that of phenyloxy containing polymers ascribed to increasing aromaticity, size, and number of aromatic rings. Photocrosslinking of stilbene containing polymers has been shown to proceed via 2p-2p cycloaddition reaction by Ultra-violet (UV) and fluorescence. The rate photocrosslinking has been found to increase with increasing number of methylene group in the main chain. The aromaticity of the side chain also increases the rate of crosslinking. POLYM. ENG. SCI., 2012. (c) 2011 Society of Plastics Engineers