Versatile Synthesis Of Liquid Crystalline Thermoplastic Elastomers

Abstract

Alkyl 4-[()-alkoxybenzoyi)oxy]benzoates(with Cl-Cloalkyl and alkoxy groups) are monotropic compounds which melt directly to isotropic liquids. Twin liquid crystalline compounds, TLCC's of [alkoxybenzoyl)oxy]benzoic acid have been synthesized. The TLCC with methoxy end groups and trioxyethylene spacer is weakly mesogenic, but replacement of the methoxy with an n-butoxy end group results in a smectic mesophase. With the decamethylene spacer, the TLCC with a methoxy end group shows a nematic mesophase, whereas the compound with n-butoxy end groups exhibits both smectic and nematic mesophases. The latter has much higher ordered liquid crystalline states than the former. The polymeric TLCP's with n-butoxy end groups and Mn=650 poly(THF) and Mn=725 poly(propylene oxide) spacers display weak liquid crystal-line order with only one mesophase transition. Decreasing the M of the poly(propylene oxide) spacer to 425 resulted in much stronger liquid crystallinenorder, exhibiting both smectic and nematic phases. It is suggested the microphase separation due to dissimilar solubility parameters can be an important contributing factor toward mesophase formation. Using this approach, TLCP's having energetic poly(hexafluoropentanediol formal) soft seg-ments have synthesized.