Liquid crystalline polymers: I. Main chain thermotropic poly(arylidene-ether)s containing cyclopentanone moiety linked with polymethylene spacers

A new series of poly(arylidene-ether)s containing cyclopentanone was synthesized by polycondensation of 4,4′-diformyl-α,ω-diphenoxyalkane 1–4 and 4,4′-diformyl-2,2′-dimethoxy-α,ω-diphenoxyalkane 5–8 with cyclopentanone. The inherent viscosity of the polymers were in the range of 0.38–1.23 dl/g. Their thermotropic liquid crystalline properties were examined by DSC, optical polarizing microscopy using a heated stage, and thermogravimetric analyses. Almost all the polymers exhibited thermotropic liquid crystalline properties. In most cases the mesophase extends up to 358°C, where the thermal decomposition prevents further observations. The polymer 14 with (n = 4), having high molecular weight, was synthesized in high yields and showed better solubility in organic solvents, such as halogenated hydrocarbons. In addition, the crystallinity of some polymers was examined by X-ray analysis, and they showed some degree of crystallinity.