Article Bionanocomposite materials from layered double hydroxide/N- trimellitylimido-L-isoleucine hybrid and poly(vinyl alcohol): Structural and morphological study Shadpour Mallakpour 1,2 and Mohammad Dinari 1,2 Abstract Nanocomposites (NCs) of poly(vinyl alcohol) (PVA) with chiral-modified magnesium– aluminum-layered double hydroxides (LDHs) were prepared by solution intercalation method. A novel chiral organomodified LDH was synthesized from the coprecipitation reaction of the aluminum (III) nitrate nonahydrate, magnesium (II) nitrate hexahydrate, and bioactive N-trimellitylimido-L-isoleucine amino acid in aqueous solution via simple, fast, and green method under ultrasound irradiation for the first time. The morphology and structure of the obtained material are examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), and field-emission SEM techniques. The TEM and XRD structure study revealed a coexis- tence of exfoliated and intercalated modified LDH in PVA matrix. The effects of modified LDH contents on the thermal property of PVA films were investigated by thermogravi- metric analysis method, and the results show that by the addition of the modified LDH into the PVA causes an increase in the thermal decomposition temperatures of the novel NC materials. 1 Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan, Islamic Republic of Iran 2 Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan, Islamic Republic of Iran Corresponding author: Shadpour Mallakpour, Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan 84 156-83111, Islamic Republic of Iran. Email: [email protected]Journal of Thermoplastic Composite Materials 1–15 ª The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0892705714530750 jtc.sagepub.com 1
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Article
Bionanocompositematerials from layereddouble hydroxide/N-trimellitylimido-L-isoleucinehybrid and poly(vinylalcohol): Structural andmorphological study
Shadpour Mallakpour1,2 and Mohammad Dinari1,2
AbstractNanocomposites (NCs) of poly(vinyl alcohol) (PVA) with chiral-modified magnesium–aluminum-layered double hydroxides (LDHs) were prepared by solution intercalationmethod. A novel chiral organomodified LDH was synthesized from the coprecipitationreaction of the aluminum (III) nitrate nonahydrate, magnesium (II) nitrate hexahydrate,and bioactive N-trimellitylimido-L-isoleucine amino acid in aqueous solution via simple,fast, and green method under ultrasound irradiation for the first time. The morphologyand structure of the obtained material are examined by X-ray diffraction (XRD), Fouriertransform infrared spectroscopy, transmission electron microscopy (TEM), andfield-emission SEM techniques. The TEM and XRD structure study revealed a coexis-tence of exfoliated and intercalated modified LDH in PVA matrix. The effects of modifiedLDH contents on the thermal property of PVA films were investigated by thermogravi-metric analysis method, and the results show that by the addition of the modified LDHinto the PVA causes an increase in the thermal decomposition temperatures of the novelNC materials.
1 Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of
Technology, Isfahan, Islamic Republic of Iran2 Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan, Islamic Republic
of Iran
Corresponding author:
Shadpour Mallakpour, Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan
University of Technology, Isfahan 84 156-83111, Islamic Republic of Iran.
residual polyene and the LDH. The neat LDH shows better thermal stability than neat PVA
and its composites. The endothermic decomposition of LDHs takes off heat from the
surrounding, and the liberated water vapor reduces the concentration of combustible
volatile in the vicinity of the polymer surface. As a result, the decomposition temperature
of the polymer is increased.50 As can be seen from Figure 5, PVA film shows 7% residue at
800�C, while the NC films show 10–17% residue at this temperature. It is notable that even
small amounts of clay were effective in improving the weight residues of the hybrids.
Morphological study. Figure 6(a) to (d) shows the TEM images of the synthesized
CO2�3 /LDH and modified LDH with CLDH with two different magnifications, respec-
tively. TEM images show smooth, well-shaped, in hexagonal form, and overlapping
crystals. For CO2�3 /LDH, TEM image shows that the sheets had a homogeneous contrast,
reflecting their ultrathin nature and uniform thickness (Figure 6(a) and (b)). For modified
LDH, the platelets have a hexagonal shape with rounded corners. There are no signs of
aggregation visible in the micrographs (Figure 5(c) and (d)). For NC of PVA and 4 wt%of CLDH, TEM observations reveal a coexistence of organonanosilicate layers in the
intercalated and partially exfoliated states. TEM micrograph shows two-dimensional
objects that are oriented largely parallel to the grid surface and thin sheet-like object with
similar lateral dimensions. The sheets have homogeneous contrast, reflecting their ultra-
thin nature and uniform thickness (Figure 6(e) and (f)).
The FESEM micrograph of CO2�3 /LDH and CLDH are shown in Figure 7. The
FESEM image of CO2�3 /LDH reveals the nature of LDH particles, which roughly con-
sists of plate-like shape stacked on top of each other with lateral dimensions ranging over
few micrometers and thickness over few hundred nanometer (Figure 7(a) and (b)). The
Figure 7. FESEM photographs of (a, b) LDH-CO2�3 and (c, d) CLDH. FESEM: field-emission scan-
ning electron microscopic; LDH: layered double hydroxide; CLDH: chiral diacid intercalatedlayered double hydroxide.
Mallakpour and Dinari 11
11
pristine CO2�3 /LDH powder consisted of small agglomerated platelets, with a sand-rose
morphology. The diacid-modified LDH powder featured much larger platelets and
they were less agglomerated than the CO2�3 /LDH particles (Figure 7(c) and (d)).
The FESEM images of neat PVA and PVA/CLDH NC4% and PVA/CLDH NC8% are
shown in Figure 8(a) to (f), respectively. According to these photographs, in the presence
of different amounts of CLDH, the morphology of PVA is changed. In the BNCs, the
micrograph exhibits good dispersion of CLDH into PVA matrix. These observations
suggested that the presence of LDH has a positive effect on PVA morphology. This
morphological change can be attributed to the reordered crystalline phase of the PVA
matrix in the presence of modified LDH, causing a packed network. It seems that the
particles are distributed uniformly in the polymer matrix.
Conclusions
Bioactive amino acids containing dicarboxylic acid was used for the preparation of the
novel organomodified CLDH in one step by coprecipitation reaction in aqueous media
Figure 8. FESEM photographs of (a, b) pure PVA, (c, d) NC4%, and (e, f) NC8%. FESEM: field-emission scanning electron microscopic; PVA: poly(vinyl alcohol); NCs: nanocomposites.
12 Journal of Thermoplastic Composite Materials
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under green conditions. CLDH was characterized by XRD, FTIR, TGA, FESEM, and
TEM techniques. The XRD results of the CLDH show that the diacid is intercalated in
the interlayer region of Mg/Al-LDH and enlarge the interlayer distance. Novel
PVA/CLDH hybrid NCs were prepared via nanoplatelet-like organic LDHs by solution
intercalation method using ultrasound energy. Three polymer/CLDH NCs were prepared
by loading different amounts of CLDH (2, 4, and 8%) into PVA matrix. The XRD and
TEM observation confirmed the formation of exfoliated microstructure of the polymer-
based NCs. The thermal stability was increased compared with the pure polymer. Since
both chiral amino acid-based dicarboxylic acid and PVA are biodegradable and biocom-
patible, the resulting hybrid organic–inorganic PVA/CLDH NCs are expected to be
biodegradable. Besides, the organic LDH nanoplatelets can be used with other polymers
for preparing exfoliated polymer/LDH NCs.
Funding
The authors wish to express their gratitude to the Research Affairs Division, Isfahan
University of Technology (IUT), Isfahan, Islamic Republic of Iran, for partial financial
support of this research. Also, the present study was financially supported by the
National Elite Foundation (NEF), Iran Nanotechnology Initiative Council (INIC), and
Center of Excellency in Sensors and Green Chemistry Research (IUT).
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