Structure and properties of fully aromatic thermotropic liquid-crystalline copolyesters containing m-hydroxybenzoic acid units


Yerlikaya Z., Aksoy S., Bayramli E.

JOURNAL OF APPLIED POLYMER SCIENCE, cilt.90, ss.3260-3269, 2003 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 90 Konu: 12
  • Basım Tarihi: 2003
  • Doi Numarası: 10.1002/app.12985
  • Dergi Adı: JOURNAL OF APPLIED POLYMER SCIENCE
  • Sayfa Sayıları: ss.3260-3269

Özet

A series of fully aromatic copolyesters based on p-acetoxybenzoic acid (p-ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA), and m-acetoxybenzoic acid (m-ABA) were prepared by a modified melt-polycondensation reaction. The copolyesters were prepared in two series in which series I is based on a two monomer system (p-ABA/m-ABA) and series II is based on a three monomer system (HQDA/TPA/m-ABA). The effect of different linear structures and kink moiety on the properties of the copolyesters were investigated systematically. The copolyesters were characterized by differential scanning calorimetry, thermogravimetric analysis, H-1-NMR, polarized optical microscopy, X-ray diffraction, and intrinsic viscosity measurements. It was found that the copolyesters exhibited nematic liquid-crystalline phases when the content of linear (p-ABA or HQDA/TPA) units was over 67 mol %. The melting or flow-transition temperatures were decreased with an increase of the content of kink m-ABA units. The copolyesters that contained p-ABA as linear units had a significantly higher degree of crystallinity compared to the copolyesters that contain HQDA/TPA as the linear units, implying a higher blockiness in the polymer chains as a result of the higher reactivity of the p-ABA units in the p-ABA/m-ABA system. All the copolyesters had poor solubility except the copolyesters containing at least 40 mol % of m-ABA, which were soluble in a dichloromethane/trifloroacetic acid (70:30 v/v) mixture. (C) 2003 Wiley Periodicals, Inc.