J IRAN CHEM SOC
1.09 nm, respectively (Fig. 6). By comparison of these
results, it can be concluded that DA1, DA3, DA4 and DA5
are vertically oriented in the interlayer space of Mg–Al
LDH. In the case of DA2, it can be presumed that two diac-
ids were placed vertically between LDH layers. By com-
parison of these data with our previous results [32], it can
be said that the position of the basal reflections of modified
samples was shifted to a higher d value for DAs contain-
ing alanine, methionine and valine amino acids intercalated
LDHs. It indicates the higher expansion in the interlayer
distance of LDHs.
analytical techniques. The XRD analysis of the DA/LDH
clays revealed that the surfactant anions were intercalated
in the interlayer region of Mg–Al LDH and thus enlarged
the interlayer distance. DAs containing alanine, methionine
and valine amino acids intercalated LDHs showed higher d
values. TG-DTG analysis exhibited the lower onset decom-
position temperatures for modified LDHs compared to the
CO32−/LDH. The presence of interlayer DA anions in LDH
was confirmed by decreasing char yields for the modified
LDHs. TEM and FE-SEM results also showed that the
original platelike particle morphology of the unmodified
LDH materials changed after organic modification, except
the appearance surface roughness and disordered edges.
This study has also opened new possibilities of investiga-
tions regarding the use of LDH type clays in polymer as
nanofiller. The improvement of LDH particle dispersion
in polymer matrix through its intercalation with efficient
surfactants such as mentioned DAs is certainly desired for
further improvement in properties, especially thermal and
mechanical properties.
Morphological analysis
The morphologies of the synthesized LDH and five diac-
ids containing LDHs prepared via ultrasonic energy were
investigated by FE-SEM and TEM techniques (Fig. 7).
Many morphologic differences between organoclay were
not observed despite the obvious variation observed in
XRD measurements. The CO32−/LDH showed the nature
of LDH particles, which roughly consists of platelike shape
stacked on top of each other with lateral dimensions rang-
ing over few micrometer and thickness over few hundred
nanometer (Fig. 7a). The morphological feature of the
organomodified LDH with chiral DAs has globular shape
in comparison with the CO23/LDH which has platelike
Acknowledgments We gratefully acknowledge the partial financial
support from the Research Affairs Division at Isfahan University of
Technology (IUT), Isfahan. The partial support of Iran Nanotechnol-
ogy Initiative Council (INIC), National Elite Foundation (NEF) and
Center of Excellence in Sensors and Green Chemistry (IUT) is grate-
fully acknowledged.
TEM presented an actual image of nanoclay platelets
to permit recognition of internal morphology of nanohy-
brids. TEM images as illustrated in Fig. 8a, b showed that
the synthesized CO32−/LDH is smooth overlapping crystal
and well-shaped in hexagonal form. Representative TEM
images of modified LDH with DA1 are shown in Fig. 8c, d.
As can be seen, DA1/LDH displayed well-defined hexago-
nal platelets with rounded corners. The sheets have homo-
geneous contrast, reflecting their ultrathin nature and uni-
form thickness. There are no signs of aggregation visible
in the micrographs (Fig. 8c, d). Better dispersion obtained
from the intercalation of LDHs by guest molecules based
on N-trimellitylimido-l-amino acids compared to the N,N-
(pyromellitoyl)-bis-l-amino acids intercalated LDHs which
was reported recently due to our previous work [32].
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In this investigation, new modified LDHs were prepared
from DAs containing bioactive amino acids by the co-
precipitation method under fast and green conditions.
DAs which were used for the intercalation process have
a good potential for biocompatibility and biodegrada-
bility. The characterization of the organically modified
Mg–Al LDH was carried out extensively using various
1 3