Hydrogen-bonded thermotropic liquid-crystalline polyester-amides from bis(hydroxy alkamido)aranes: Synthesis and properties

Abstract

Hydrogen-bonded aromatic–aliphatic polyester–amides (PEAs) were prepared by solution/melt polycondensation of aromatic–aliphatic amidodiols 1,4-bis(4-hydroxybutyramide)benzene (BHBB), 1,4-bis(5-hydroxy pentamide)benzene, 1,4-bis(6-hydroxyhexamide)benzene, 1,4-bis(4-hydroxybutyramidexylene), 1,4-bis(5-hydroxypentamidexylene, 1,4-bis(4-hydroxybutyramide)benzene, and 1,4-bis(6-hydroxyhexamidexylene) with terephthaloyl chloride/dimethyl terephthalate. Aromatic–aliphatic amido diols were prepared by the aminolysis of γ-butyrolactone, δ-valerolactone, and ϵ-caprolactone with aromatic diamines such as paraphenylene diamine and paraxylene diamine. The monomers and polymers were characterized by chemical analysis (hydroxyl value and elemental analysis), Fourier transform infrared spectroscopy, 1H NMR, and 13C NMR. The thermal- and phase-transition behaviors of the polymers were investigated by differential scanning calorimetry in combination with hot-stage optical microscopy. Crystallinity of polymers was examined with wide-angle X-ray diffraction. The polymers exhibited liquid crystallinity with layered structures formed by self-organization of the hetero intermolecular hydrogen-bonded networks indicating smectic phases except for PEAs prepared from BHBB. The hydrogen atom of the phenyl-substituent group forces the neighboring carbonyl groups out of plane of the rings preventing formation of layered structures in the case of BHBB. The PEAs retained intermolecular hydrogen bonding even in the mesomorphic state, and variations in the hydrogen-bonded lamellae/micelles might be responsible for the variations from one smectic to another texture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 335–346, 2003