The structure of noncrystalline phase component in a thermotropic liquid-crystalline copolyester

Temperature-induced evolution of the structure of noncrystalline phase comp onents in the oriented fibers of a thermotropic liquid-crystalline (LC) ran dom-chain copolyester was studied by X-ray diffraction and differential sca nning calorimetry. The polymer contains three monomer components, including (i) a triad composed of the hydroxybenzoic, terephthalic, and hydroxybenzo ic acid residues, (ii) phenylhydroquinone, and (iii) resorcin, taken in var ious proportions. The samples of copolyester were prepared in the form of o riented fibers melt-spun at 350 degrees C and rapidly cooled to room temper ature. Copolymers annealed at temperatures above the glass transition tempe rature exhibited a very low crystallization rate. Almost complete absence o f the crystalline phase in the samples allowed temperature-induced variatio n of the structure of a noncrystalline phase component to be followed, whic h has proven to be stable in a very broad temperature interval (20-320 degr ees C). The noncrystalline material possesses a two-phase LC structure, com prising a typical nematic phase and a polymer mesophase of a new type, the so-called aperiodic smectic phase.