Liquid Crystal Polymers: VI. Liquid Crystalline Polyesters of Substituted Hydroquinones

The use of monosubstituted hydroquinones enables the preparation of liquid crystalline polyesters with lower melting points than can be obtained with hydroquinone. When the substituent is chloro, methyl, tert-butyl, or 1,1-dimethylhexyl, the polyterephthalate homopolyesters still melt at too high a temperature to be injection-molded or melt spun without thermal degradation, but additional modification with a flexible aliphatic component, a kinked rigid group, or 2,6-naphthalenedicarboxylic acid reduces the melting point further and enables the preparation of melt processable liquid crystalline polyesters. The stability of substituted hydroquinone polyesters in air at 150ºC decreases with various substituents in the order of phenyl, tert-butyl, chloro, methyl. At 300ºC in air, the hydroquinone polyesters containing phenyl or tert-butyl substituents are the most stable. The effects of composition on liquid crystallinity and on the properties of injection-molded plastics and melt spun fibers also are discussed.