A novel series of main chain liquid crystalline copolyesters with X-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4

4-bis(4-hydroxyphenylazo) dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4

4-(a

w-hexanedioyloxy) dibenzoyl dichloride (M1)

2

5-bis(p-octyloxybenzoyloxy) hydro-quinone (M2) and cis-4

4-bis(4-hydroxyphenylazo) dibenzo-18-crown-6 (M3). Monomer M1 was synthesized by esterification and substitution of adipoyl chloride with p-hydroxybenzoic acid

monomer M2 was synthesized by esterfication and reduction reaction of 2

5-dihydroxybenzoquinone and p-octanoxybenzoyl chloride and monomer M3 was synthesized by diazotization and coupling reaction of cis-diaminodibenzo-18-crown-6 with phenol. The molecular weights of copolyesters are not high

and the intrinsic viscosity [h] of copolyesters ranges from 0.25-0.35. The monomers’ structures were identified by using elemental analysis

IR

UV

1H-NMR

MS

etc. All the copolyesters are yellowish powders and insoluble in THF and CHCl3 at room temperature except CP9. The properties of copolyesters were investigated by using GPC

[h]

DSC

TG

WAXD and POM. It was found that all the copolyesters entered into liquid crystal phase when they were heated to above their melting temperature (Tm). The typical smectic and nematic phase texture can be observed on POM. Their mesophase transition temperature and thermal stability change regularly with varying the content of cis-4

4-bis(4-hydroxyphenylazo) dibenzo-18-crown-6 unit in the copolyesters.