Liquid-crystalline polyethers based on conformational isomerism. Part 33.–Thermotropic polyethers based on a mesogenic group containing rigid and flexible units: 1-(4′-hydroxybiphenyl-4-yl)-2-(4-hydroxyphenyl)propane

Abstract

The synthesis of a mesogenic group containing rigid and flexible units: 1-(4′-hydroxybiphenyl-4-yl)-2-(4-hydroxy-phenyl)propane (TPP) is presented. TPP was polyetherified under phase-transfer catalysed conditions with α,ω-dibromoalkanes containing 4–20 methylenic units. The resulting polyethers, TPP-x(where x= number of methylenic groups in the spacer), were characterized by a combination of techniques consisting of differential scanning calorimetry, thermal optical polarized microscopy and small- and wide-angle X-ray scattering experiments. All TPP-x polyethers displayed multiple crystalline phases whose nature was determined by the spacer length. TPP-x with x of less than 9 exhibited crystalline phases in which the mesogenic and spacer were intermeshed. Polymers with longer spacers displayed crystalline phases in which the mesogen and spacer were separated in separate layers of different electron densities. TPP-x with x= 5, 7, 9 and 11 also exhibited a nematic mesophase.