Abstract
Nanocomposites of three thermotropic liquid crystalline polymers (TLCPs)
with organoclay were prepared. The first TLCP, poly(2-ethoxyhydroquinone2-bromoterephthaloyl), EHBT, consists of wholly aromatic ester type mesogenic units containing an ethoxy side group, and the second poly(oxybiphenyleneoxy-2,5-dihexyloxyterephthaloyl) (OBDT) is an aromatic polyester
TLCP having alkoxy side groups on the terephthaloyl moiety. The last
TLCP polyazomethine (PAM) consists of diad aromatic azomethine type
mesogenic units. An EHBT with an alkoxy side-group was synthesized from
2-ethoxyhydroquinone and 2-bromoterephthalic acid. Nanocomposites of
EHBT with Cloisite 25A (C25A) as an organoclay were prepared by the
melting intercalation method above the melt temperature (T m ) of the TLCP.
Liquid crystallinity, morphology, and thermo-mechanical behaviors were
examined with increasing organoclay content from 0 to 6 wt%. Liquid crystallinity of the C25A/EHBT hybrids was observed when organoclay content was
up to 6 wt%. Regardless of the clay content in the hybrids, the C25A in EHBT
was highly dispersed in a nanometer scale. The hybrids (0–6 wt% C25A/
EHBT) were processed for fiber spinning to examine their tensile properties.
Ultimate strength and initial modulus of the EHBT hybrids increased with
increasing clay content and the maximum values of the mechanical properties
were obtained from the hybrid containing 6 wt% of the organoclay. A TLCP
(OBDT)/organoclay nanocomposite was synthesized via in-situ intercalation
polycondensation of diethyl-2,5-dihexyloxyterephthalic acid and 4,40 -biphenol in the presence of organically modified montmorillonite (MMT).
The organoclay, C18–MMT, was prepared by the ion exchange of Na
+
–MMT
with octadecylamine chloride (C18–Cl
À ). OBDT/C18–MMT nanocomposites
were prepared to examine the variations of the thermal properties, morphology,
and liquid crystalline phases of the nanocomposites with clay content in the
range 0–7 wt%. It was found that the addition of only a small amount of
organoclay was sufficient to improve the thermal behavior of the OBDT
hybrids, with maximum enhancement being observed at 1 wt% C18–MMT.
Nanocomposites of PAM with the organoclay C12-MMT were also synthesized
by using the in-situ interlayer polymerization method. The variations with
organoclay content of the thermal properties, morphology, and liquid crystalline mesophases of the hybrids were determined for concentrations from
0 to 9 wt% C12-MMT. The wide-angle X-ray diffraction (XRD) analysis and
transmission electron microscope (TEM) micrographs show that the levels of
nanosize dispersion can be controlled by varying the C12-MMT content. The
clay particles are better dispersed in the matrix polymer at low clay contents
than at high clay contents. With the exception of the glass transition temperature (T g ), the maximum enhancement in the thermal properties was found to
arise at an organoclay content of 1 wt%. Further, the PAM hybrids were shown
to exhibit a nematic liquid crystalline phase for organoclay contents in the
range 0–9 wt%.
578
T. Y. Ha et al.
Nanocomposites of three thermotropic liquid crystalline polymers (TLCPs)
with organoclay were prepared. The first TLCP, poly(2-ethoxyhydroquinone2-bromoterephthaloyl), EHBT, consists of wholly aromatic ester type mesogenic units containing an ethoxy side group, and the second poly(oxybiphenyleneoxy-2,5-dihexyloxyterephthaloyl) (OBDT) is an aromatic polyester
TLCP having alkoxy side groups on the terephthaloyl moiety. The last
TLCP polyazomethine (PAM) consists of diad aromatic azomethine type
mesogenic units. An EHBT with an alkoxy side-group was synthesized from
2-ethoxyhydroquinone and 2-bromoterephthalic acid. Nanocomposites of
EHBT with Cloisite 25A (C25A) as an organoclay were prepared by the
melting intercalation method above the melt temperature (T m ) of the TLCP.
Liquid crystallinity, morphology, and thermo-mechanical behaviors were
examined with increasing organoclay content from 0 to 6 wt%. Liquid crystallinity of the C25A/EHBT hybrids was observed when organoclay content was
up to 6 wt%. Regardless of the clay content in the hybrids, the C25A in EHBT
was highly dispersed in a nanometer scale. The hybrids (0–6 wt% C25A/
EHBT) were processed for fiber spinning to examine their tensile properties.
Ultimate strength and initial modulus of the EHBT hybrids increased with
increasing clay content and the maximum values of the mechanical properties
were obtained from the hybrid containing 6 wt% of the organoclay. A TLCP
(OBDT)/organoclay nanocomposite was synthesized via in-situ intercalation
polycondensation of diethyl-2,5-dihexyloxyterephthalic acid and 4,40 -biphenol in the presence of organically modified montmorillonite (MMT).
The organoclay, C18–MMT, was prepared by the ion exchange of Na
+
–MMT
with octadecylamine chloride (C18–Cl
À ). OBDT/C18–MMT nanocomposites
were prepared to examine the variations of the thermal properties, morphology,
and liquid crystalline phases of the nanocomposites with clay content in the
range 0–7 wt%. It was found that the addition of only a small amount of
organoclay was sufficient to improve the thermal behavior of the OBDT
hybrids, with maximum enhancement being observed at 1 wt% C18–MMT.
Nanocomposites of PAM with the organoclay C12-MMT were also synthesized
by using the in-situ interlayer polymerization method. The variations with
organoclay content of the thermal properties, morphology, and liquid crystalline mesophases of the hybrids were determined for concentrations from
0 to 9 wt% C12-MMT. The wide-angle X-ray diffraction (XRD) analysis and
transmission electron microscope (TEM) micrographs show that the levels of
nanosize dispersion can be controlled by varying the C12-MMT content. The
clay particles are better dispersed in the matrix polymer at low clay contents
than at high clay contents. With the exception of the glass transition temperature (T g ), the maximum enhancement in the thermal properties was found to
arise at an organoclay content of 1 wt%. Further, the PAM hybrids were shown
to exhibit a nematic liquid crystalline phase for organoclay contents in the
range 0–9 wt%.
578
T. Y. Ha et al.