existing state of the clay particles affects the thermal behaviors and tensile mechanical properties of each organoclay/polymer hybrid.
Figure 8 shows SEM images of the fractured surfaces of the OBDT hybrids
containing 0–7 wt% organoclay. Figure 8b shows that clay phases form in the
OBDT hybrids: the hybrid with 1 wt% C18-MMT has morphologies consisting
of clay domains that are well dispersed in a continuous TLCP phase. In contrast,
the micrographs of the 5 and 7 wt% C18-MMT/OBDT hybrid (Fig. 8d, e,
respectively) show voids and deformed regions that can be attributed to the
coarseness of the fractured surface. The fractured surfaces were more deformed
when the hybrids contained more organoclay, likely as a consequence of agglomeration of clay particles. Figure 9 shows TEM photographs of the OBDT hybrid
containing 1 wt% C18-MMT. Some of the clay is dispersed well in the OBDT
matrix, and some is agglomerated to a size of approximately 10–20 nm. As in the
case of 5 wt% C18-MMT (see Fig. 10), these clays are for the most part
agglomerated in the polymer matrix. The peaks in the XRD patterns of these
samples should be attributed to these agglomerated layers (see Fig. 4). Unlike the
hybrids containing 1 wt% C18-MMT, the clay layers of the 5 wt% hybrid are not
intercalated into the matrix polymer, consistent with the XRD and SEM data in
Figs. 4 and 8, respectively. Agglomeration of the dispersed clay phase clearly
increases with increasing organoclay content. It is conceivable that the agglomerated clay domain may decrease the thermal properties of the hybrids, probably
because of poor interfacial adhesion between the organoclay and the TLCP
hybrid matrix.
The TEM micrographs in Figs. 11 and 12 show the morphologies of PAM hybrids
at different magnifications. Figure 11 (1 wt% C12-MMT/PAM) shows that
C12-MMT is well dispersed in the polymer matrix at all magnification levels,
although some agglomerated particles have formed. For the 5 wt% hybrid
(Fig. 12), some of the clay is well dispersed within the PAM matrix, and the
remainder is present in agglomerations. The average diameter and length of the
clays in Figs. 11 and 12 are 5–10 nm and 10–20 nm, respectively. As previously
mentioned, the TEM results indicate that at low organoclay contents, the clays are
well dispersed throughout the PAM matrix and that agglomerated structures
are evident at higher clay contents. The peaks in the XRD patterns of these samples
are attributed to these agglomerated layers (see Fig. 5).
Thermal Behaviors
The thermal properties of EHBT hybrids with different organoclay contents are
listed in Table 1. The glass transition temperatures (T g ) of EHBT hybrids increased
linearly from 92 to 98
C with clay loading from 0 to 4 wt% and leveled off at more
than 4 wt% of organoclay. The increase in the T g value of these hybrids could be the
result of two factors (Agag et al. 2001). First, the effect of small amounts of
dispersed clay layers on the free volume of TLCP is significant and does influence
the glass transition temperature of TLCP hybrids. The second factor is ascribed to
21 Characterizations of Nanocomposites of Liquid Crystalline Polymers
593
Figure 8 shows SEM images of the fractured surfaces of the OBDT hybrids
containing 0–7 wt% organoclay. Figure 8b shows that clay phases form in the
OBDT hybrids: the hybrid with 1 wt% C18-MMT has morphologies consisting
of clay domains that are well dispersed in a continuous TLCP phase. In contrast,
the micrographs of the 5 and 7 wt% C18-MMT/OBDT hybrid (Fig. 8d, e,
respectively) show voids and deformed regions that can be attributed to the
coarseness of the fractured surface. The fractured surfaces were more deformed
when the hybrids contained more organoclay, likely as a consequence of agglomeration of clay particles. Figure 9 shows TEM photographs of the OBDT hybrid
containing 1 wt% C18-MMT. Some of the clay is dispersed well in the OBDT
matrix, and some is agglomerated to a size of approximately 10–20 nm. As in the
case of 5 wt% C18-MMT (see Fig. 10), these clays are for the most part
agglomerated in the polymer matrix. The peaks in the XRD patterns of these
samples should be attributed to these agglomerated layers (see Fig. 4). Unlike the
hybrids containing 1 wt% C18-MMT, the clay layers of the 5 wt% hybrid are not
intercalated into the matrix polymer, consistent with the XRD and SEM data in
Figs. 4 and 8, respectively. Agglomeration of the dispersed clay phase clearly
increases with increasing organoclay content. It is conceivable that the agglomerated clay domain may decrease the thermal properties of the hybrids, probably
because of poor interfacial adhesion between the organoclay and the TLCP
hybrid matrix.
The TEM micrographs in Figs. 11 and 12 show the morphologies of PAM hybrids
at different magnifications. Figure 11 (1 wt% C12-MMT/PAM) shows that
C12-MMT is well dispersed in the polymer matrix at all magnification levels,
although some agglomerated particles have formed. For the 5 wt% hybrid
(Fig. 12), some of the clay is well dispersed within the PAM matrix, and the
remainder is present in agglomerations. The average diameter and length of the
clays in Figs. 11 and 12 are 5–10 nm and 10–20 nm, respectively. As previously
mentioned, the TEM results indicate that at low organoclay contents, the clays are
well dispersed throughout the PAM matrix and that agglomerated structures
are evident at higher clay contents. The peaks in the XRD patterns of these samples
are attributed to these agglomerated layers (see Fig. 5).
Thermal Behaviors
The thermal properties of EHBT hybrids with different organoclay contents are
listed in Table 1. The glass transition temperatures (T g ) of EHBT hybrids increased
linearly from 92 to 98
C with clay loading from 0 to 4 wt% and leveled off at more
than 4 wt% of organoclay. The increase in the T g value of these hybrids could be the
result of two factors (Agag et al. 2001). First, the effect of small amounts of
dispersed clay layers on the free volume of TLCP is significant and does influence
the glass transition temperature of TLCP hybrids. The second factor is ascribed to
21 Characterizations of Nanocomposites of Liquid Crystalline Polymers
593