Thermotropic liquid crystalline polyphenylphosphates containing aryl ester mesogens

Abstract

AbstractA series of main‐chain liquid crystalline polyphosphate esters with varying center core in a triad ester mesogen were prepared. The phosphorus is incorporated in the middle of the spacer unit. All the monomers and polymers were characterized by spectral and thermal techniques. Thermogravimetric analysis shows that these polymers were stable up to 295–340°C. The char yields of the polymer were in range of 11–31%. Differential scanning calorimetry (DSC) thermal analysis confirms the mesophase formation of the polymers. Some of the polymers exhibited micro‐grainy textures with low glass transition. The DSC and microscopic analysis reveal that the polymer containing central unit which increases the aspect ratio shows liquid crystalline properties, whereas the unit that decreases the aspect ratio failed to show the mesophase formation. Energy minimized structures for the mesogenic units reveal that the polymers containing phenyl, pyridazine, diphenyl ester, and biphenyl unit shows high aspect ratio compared to nonmesogenic phenolphthalein, bisphenol‐A, and bisphenol‐S units. It revealed that increasing the length of the mesogen and incorporating heteroatoms in the aromatic moiety increased the mesophase stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3924–3930, 2007