Monotropic liquid crystal behavior in two poly(ester imides) with even and odd flexible spacers

Abstract

Mesophase behavior of two poly(ester imides) synthesized from N-[4-(chloroformyl)phenyl]-4-(chloroformyl)phthalimide and 1,4-butanediol or 1,9-nonanediol has been extensively studied. One of the polymers has four methylene units (even) and the other nine methylene units (odd) in its respective flexible spacers. Both polymers show monotropic liquid crystal behavior which has been identified by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and polarized light microscopy (PLM) experiments. The liquid crystal phase seems to be more ordered than the nematic phase. Further crystallization from this liquid crystal phase can be achieved during cooling and/or isothermal experiments below the isotropic melt to liquid crystal transition temperature. This indicates that the molecules in the liquid crystal phase possess high mobility. Isothermal experiments on these polymers at temperatures above the monotropic liquid crystal transition lead to direct crystallization from the isotropic melt with large axilitic or spherulitic texture.

A solid-state13C-NMR study of the mesophases of PEIM-9 (poly(4,4′-phthaloimidobenzoylnonamethylene-oxycarbonyl))

“…Two melting transitions in the differential scanning calorimetry (DSC) heating traces correspond to these two phases (415 and 437 K, respectively). In order to correspond to these earlier results, the NMR spectra of the present work were taken on the same samples, and at the same temperatures as in the earlier studies [1]. In the NMR experiments dipolar decoupling of protons and magic angle spinning give high-resolution spectra.…”

“…In this paper, a high-resolution 13 C solid-state NMR analysis at variable temperatures is described for a PEIM synthesized from 4-(4'-chlorocarbonyl)-phthalimidobenzoyl chloride and 1,9-nonanediol (poly(4,4'-phthaloimidobenzoylnonamethyleneoxycarbonyl)) [1] (PEIM-9). The goal was to identify molecular conformation and motion at specific sites of the repeating unit in its different phases.…”

“…This PEIM-9 had been studied earlier by differential scanning calorimetry (DSC), wideangle X-ray diffraction (WAXD), and polarizedlight and transmission electron microscopies (PLM and TEM) [1]. It was shown that PEIM-9 changes on cooling from the isotropic melt to a metastable, monotropic, smectic liquid crystal (LC) at 369.2 K. Annealing for more than 60 min at 365 K leads to further ordering proving the metastable nature of the liquid crystal phase.…”

“…The preparation of PEIM-9 involved coupling of 4-(4'-chlorocarbonyl)-phthalimidobenzoyl chloride and 1,9-nonanediol. Sample characterizations were reported [1]. The intrinsic viscosity is 0.6 dl/g.…”

“…The molecular mass of the repeating unit is 435 Da. The same sample as described in [1] is used in this study. Therefore, DSC data reported earlier in [1] will be used in this paper for discussion.…”