CC BY
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ISSN 2522-1841 (Online) AZERBAIJAN CHEMICAL JOURNAL № 1 2023 141
ISSN 0005-2531 (Print)
UDC 541.73:547.458.81
THE SONOCHEMICAL SYNTHESIS OF PVA/Mg-Al-OH LAYERED DOUBLE HYDROXIDE NANOCOMPOSITE FILM
KhA.Ibrahimova1, A.A.Azizov1, O.O.Balayeva1, R.M.Alosmanov\ M.H.Abbasov2
1Baku State University
2M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education
of the Republic of Azerbaijan
Received 20.06.2022 Accepted 29.09.2022
In this study, we report the synthesis of PVA/Mg-Al-OH layered double hydroxide composite film by a sonochemical method under different reaction proceedings. The prepared nanocomposites were characterized by X-ray powder diffraction analysis (XRD), Ultraviolet-visible (UV-Vis) spectroscope, Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscope (EDS), and Fourier transform infrared (FTIR) spectroscopes to study structural, optical, and morphological properties. The basal spacing of PVA/Mg-Al-OH composite increased from 7.694Â to 8.424 Â and the basal spacing of layered double hydroxide enlarged after PVA attached to the surface effects. The average size of particles was determined 23.4 and 4.48 nm. The decrease of particle size explained by the influence of organic groups on the stability of the structure. The optical band gap of PVA/Mg-Al-OH layered double hydroxide was estimated to be 0.64 eV and 0.9 eV, respectively.
Keywords: polyvinyl alcohol, layered double hydroxide, sonochemical synthesis, polymer composite.
like Mg2+, Fe2+, Zn2+, Cu2+, M(III) denotes tri-valent cations such as Al3+, Cr3+, Fe3+, An- is the anion, x is the amount of the trivalent metal ion, and m is the water molecules.
LDH has also known as a new class of the most promising layered materials incorporated into polymer matrices as reinforcing filler [7]. When LDH being included in polymer matrices and properties of the prepared nanocom-posites can be improved the thermal stability, flame retardancy, mechanical, and rheological properties [8]. Among numerous kinds of LDHs, Mg-Al-LDHs are the earliest and extensively researched products [9].
Recently, PVA-based nanocomposites have been composed to improve PVA properties and further explore its applications by the solution casting method [10]. Polyvinyl alcohol (PVA) is a water-soluble polymer frequently used as a colloid stabilizer [11]. The introduction of stabilizers influences the chemical properties as well as the physical properties of semiconductor materials, from stability, solubility, and light emission [12].
doi.org/10.32737/0005-2531-2023-1-141-148
Introduction
Polymer nanocomposites is a class of material because of various unique properties such as improved mechanical properties, gas barrier properties, increased heat distortion temperature, reduced solvent uptake, and lower flammability [1].
Last decade, layered double hydroxides (LDHs) have attracted much attention due to their easily manipulating properties and potential applications such as ion exchangers, polymer stabilizers, adsorbent catalysts [2], and their support [3], electrodes, and biomedical drug delivery [4]. Layered double hydroxides known as anion-ic clays or hydrotalcite-like materials have attracted enormous interest due to their many applications like anion exchangers, base catalysts, metal oxides precursors, PVC additives [5]. This general formula using can be described of LDHs materials [6]:
[M(II)i-XM(III)X(OH)2](AX-) • mH2O.
n
Where, M(II) represents divalent cations
Fig. 1. Schematic illustration of the synthesis procedure of PVA/Mg-Al-OH layered double hydroxide
nanocomposite film.
In this context, we report the synthesis of PVA/Mg-Al-OH layered double hydroxide composite film by a sonochemical method. The results obtained from X-ray, SEM, EDX, UV-Vis, and FTIR spectroscopy experiments are reported.
Experimental part
Materials and instrumentation
All chemicals magnesium hydroxide [Mg(OH)2], aluminum hydroxide [Al(OHb], polyvinyl alcohol (PVA), lead(II)acetate trihydrate [PHCH3COOV3H2O] and sodium sulfide nonahydrate [Na2S-9H2O] were of analytical grade. All the experiments were used distilled water.
The preparation of pure meixnerite (Mg-Al-OH-type of layered double hydroxide) composite
A one-step mechanochemical method was used to prepare the meixnerite (Mg-Al-OH) type of LDH. 2 g of Mg(OH)2 and Al(OH)3 at a molar ratio of 3:1 was mixed and mechanically ground in a mortar. Synthesis of LDH sample was conducted by dispersing 1 g of grounded samples in 100 ml water at room temperature and agitating for 4h on the magnetic stirrer and air-dried.
The synthesis of PVA/Mg-Al-OH thin film
Bath type ultrasonicator (VCX500) was used for the synthesis of PVA/Mg-Al-OH film.
For the prepared film, 4 g of PVA was dissolved in 40 ml distilled water. 0.3 g of Mg-Al-OH composite was added into 10 ml 10% PVA solution and ultrasonically stirred for 10
min at room temperature. The solution was dried at room temperature.
Characterization
Powder X-ray diffractometer (XRD) (Bruker D2 Phaser) in CuKa radiation (X= 0.1541 nm) was used in the angular range 20=10-80° to characterize the structural properties of the samples.
Optical characterization was carried out by Specord 210 plus UV-Vis spectrometer.
JEOL ISM-7600F Scanning electron microscope (SEM) and X-max 50 energy dispersive X-ray spectrometer (EDX) were used to characterize the surface morphology and chemical composition of the products.
Fourier-transform infrared spectroscopy (FT-IR) spectra were recorded within 500-4000 cm-1 region on a NICOLET IS10 FTIR spectrometer.
Results and discussion
Structural properties
Figure 2 shows the XRD pattern in the range of 10-80° of the Mg(OH)2 and Al(OH)g mixture mechanically ground in a mortar for a 3 h one-step ground operation.
The characteristic reflection planes (003), (006), (009), (012), and (110) corresponding to hydrotalcite-like crystal structures [13] of meixnerite type of LDHs were clearly observed to appear in the milled products, however, peaks of starting materials remain in the milled mixtures. The peak intensity decreases with a further increase in milling time [14].
Fig. 2. XRD pattern of a) Mg-Al-OH, b) PVA/Mg-Al-OH nanocomposite film.
The formation of meixnerite (Mg-Al-OH) or Mg6[Ah(OH)18-5.5H2O could be shown by the following reaction (1)
2Al(OH)3(actiVe) + 6Mg(OH)2(actiVe) + 5.5H2O ^ [Mg6Al2(OH)i8 • 5.5H2O (1)
Additional structural parameters can be obtained by examining changes in the d (003) spacing of the LDH. The d(003) spacing of an LDH corresponds to the distance between the cation layers. When the interlayer anion in an LDH is changed, a corresponding change in the basal spacing should be observed. This change will indicate if the new anions have been successfully intercalated into the LDH
or simply adsorbed onto the surface of the material.
XRD pattern of PVA/Mg-Al-OH composite film prepared by the sonochemical method are shown in [Figure 1 (curve (1))]. PVA is a crystalline polymer and the diffraction peak at 2 =19.98 correspond to that of the PVA monoclinic crystalline phase [15].
The basal spacing of LDH is determined by Bragg's Law equation from (003) reflection [16].
d
nÀ 2stn0
(2)
Where 0 is the scattering angle, n is a positive integer and X is the wavelength of the incident wave.
Table 1. Structural parameters of meixnerite (Mg-Al-OH) and polymer composite determined from the XRD pattern
Parameters (A°) Mg-Al-OH PVA/Mg-Al-OH
d(003) 7.694 8.424
d(110) 1.518 1.565
a-2dn3 - (latt.par) 3.06 3.13
c-3d003 - (latt. par.) 23.082 25,272
D - (particle size) nm 23.4 4.48
The basal spacing of PVA/Mg-Al-OH composite increased from 7.694A to 8.424 A and the basal spacing of LDH enlarged after PVA attached to the surface effects (Table 1). In water, most hydroxyl groups of PVA chains can form inter- and intra-molecular hydrogen bonds, which affect the hydration state and dynamics of PVA macromolecules in the solution [17]. The LDH layers can then be adsorbed into PVA chains by interacting with the free OH groups of PVA chains that do not participate in the formation of hydrogen bonds [18]. The average size of particles was determined 4.48 nm.
The average size of nanoparticles has been calculated using Debye-Scherrer equation [20].
D =
aX Pcos8
(3)
Where D is the particle diameter, a is the Scher-rer constant (0.9), X is the X-ray wavelength (0.15418 nm), p is the full width of half maximum (FWHM) and 0 is the Bragg's angle.
Optical studies
UV-Vis absorption spectra were used to characterize the electronic properties of the synthesized materials. Mg-Al-OH exhibited a quite low absorbance in the range of 200-800 nm [Figure 3 (curve (1))]. As shown in [Figure 3 (curve (2))], the absorption threshold of PVA/Mg-Al-OH composite was about 350 nm. The absorption of light for a material occurs by the transfer of electrons from the valence band to the conduction band.
The optical absorption spectra analysis in solid material provides essential information about the band structure and the energy band gap in the materials.
Fig. 3. UV-Vis absorption spectra of 1) Mg-Al-OH; 2) PVA/Mg-Al-OH composite film.
Fig. 4. UV-Vis calculated band gap of a) Mg-Al-OH; b) PVA/Mg-Al-OH composite film. Table 2. The band gap value and particle size of the synthesized samples
Samples Bandgap values Particle sizes (nm)
Mg-Al-OH 0.68 eV; 0.75 eV 23.4
PVA/Mg-Al-OH 0.64 eV; 0.9 eV 4.48
At.(%)
30.90 l 0.06 g 199 1.29 65.76
600Mitm
Fig. 5. SEM images, EDX mapping images and EDX pattern of PVA/Mg-Al-OH nanocomposite film.
Fig. 6. FT-IR spectra of PVA/Mg-Al-OH composite film.
Morfological analyses by SEM
In order to investigate the morphology of the composites, SEM microphotographs of the synthesized nanocrystals were shown in Figure 5.
The SEM micrographs obtained clearly show that these plate-like particles are composed of hexagonally shaped nanoparticles that are characteristic of LDH structures [21]. We observed large and lumpy particles in the photo.The surface morphology of the synthesized polymer composite sample exhibits agglomeration [22] of fine particles in several microns, though the size of primary particles is in nanoscale.
FT-IR spectroscopy study
The synthesized samples were characterized by recording their FT-IR spectra in the range of 500-4000 cm-1 [Figure 6]. The spectra exhibited characteristic bands of stretching and bending vibrations of the functional groups formed in the prepared films.
The infrared bands at 3270-3740 cm-1 are attributed to the stretching vibration of OH group. The peak at a higher position corresponds to the free OH group of the starting
hydroxide samples. It is the evidence for the presence of LDH in the PVA matrix, O-H bending peaks were observed at 1555 cm-1 and 1421 cm-1, and C-H stretching peaks were observed at 2924 cm-1 and 2783 cm-1 (Figure 5). These peaks are very intense and broad. This may because both the matrix polyvinyl alcohol and the nanoparticles layered double hydroxide are hydroxyl materials. This band is recognized as crystallization sensitive band of the PVA matrix.
Conclusion
In this paper, we have discussed the synthesis of PVA/Mg-Al-OH layered double hydroxide composite film by the sonochemical method at room temperature. XRD study shows a basal spacing of PVA/Mg-Al-OH composite increased from 7.694Â to 8.424 Â and the basal spacing of LDH enlarged after PVA attached to the surface effects. The average size of particles was determined 23.4 nm and 4.48 nm.
FT-IR analysis showed that the peak at a higher position corresponds to the free OH group of the starting hydroxide samples and it is the evidence for the presence of LDH in the PVA matrix.
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PVS/Mg-Al-OH LAYLI iKiLi HiDROKSiD NANOKOMPOZiT TOBOQOSiNiN
SONOKlMYOVi SiNTEZi
X.A.ibrahimova, A.O.Ozizov, O.O.Balayeva, R.M.Alosmanov, M.H.Abbasov
Taqdim olunan ijda PVS/Mg-Al-OH layli ikili hidroksid nanokompozit tabaqasinin müxtalif reaksiya ¡jaraitlarinda sonokimyavi üsulla sintezi haqqinda malumat verilir. Alinmij nümunalarin quruluj xüsusiyyatlarini, optiki xassalarini va morfoloji qurulujunu xarakteriza etmak ügün Rentgen toz difraktometri (RTD), Ultrabanövjayi-gör. (UB-gör) spektrometr, Skanedici Elektron mikroskop (SEM), Enerji-dispersiv rentgen spektrometr (EDS) va Furye dayijdiricisi
olan infraqirmizi (lQ) spektrometrdan istifada edilmi§dir. PVS/Mg-Al-OH kompozitinda polivinil spirtinin satha birla§masindan sonra layli ikili hidroksidin laylararasi masafasi 7.694A-dan 8.424A-a qadar geni§lanmi§dir. Hissaciklarin orta olgusu 23.4 va 4.48 nm muayyan edilmi§dir. Hissaciklarin olgusunun azalmasi uzvi qruplarin strukturun dayaniqligina tasiri ila izah olunu. PVA/Mg-Al-OH layli ikiqat hidroksidin optik qadagan olunmu§ zolagin eninin enerjisi muvafiq olaraq 0.64 eV va 0.9 eV hesablanmi§dir.
Agar sozlzr: polivinil spirti, qatli ikili hidroksid, sonokimyavi sintez, polimer kompozit.
СОНОХИМИЧЕСКИЙ СИНТЕЗ ПВС/Mg-Al-OH СЛОИСТОЙ ДВОЙНОЙ ГИДРОКСИДНОЙ
НАНОКОМПОЗИТНОЙ ПЛЕНКИ
Х.А.Ибрагимова, А.А.Азизов, О.О.Балаева, Р.М.Алосманов, М.Г.Аббасов
В этом исследовании мы сообщаем о синтезе слоистой двойной гидроксидной композитной пленки ПВС/Mg-Al-OH сонохимическим методом при различных реакционных процедурах. Приготовленные нанокомпозиты были охарактеризованы с помощью рентгеноструктурный анализа (РСА), спектроскопии в ультрафиолетовой и видимой областях (УФ/Вид), сканирующего электронного микроскопа (СЭМ), энергодисперсионного рентгеновского спектроскопа (ЭДС) и инфракрасного преобразования Фурье (ИКФС). ) спектроскопы для изучения структурных, оптических и морфологических свойств. В композите ПВС/Mg-Al-OH межслоевое расстояние слоистого бинарного гидроксида увеличилось с 7.694 А до 8.424 А после добавления на поверхность поливинилового спирта. Определен средний размер частиц 23.4 и 4.48 нм. Уменьшение размера частиц объясняется влиянием органических групп на стабильность структуры. Оптическая ширина запрещенной зоны двойного слоистого гидроксида ПВС/Mg-Al-OH оценивается как 0.64 эВ и 0.9 эВ соответственно.
Ключевые слова: поливиниловый спирт, слоистый двойной гидроксид, сонохимический синтез, полимерный композит.
