Water-soluble stable polymer nanocomposites with AuNPs based on the functional poly(1-vinyl-1,2,4-triazole-co-N-vinylpyrrolidone)

Article abstract of DOI:10.1016/j.jorganchem.2020.121352

New water-soluble polymer nanocomposites with gold nanoparticles (AuNPs) were synthesized using functional copolymer of 1-vinyl-1,2,4-triazole with N-vinylpyrrolidone (poly(VT-co-VP)) as a stabilizing matrix. The polymer AuNPs nanocomposites were studied by transmission electron microscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, atomic absorption and thermogravimetric analysis. The gold content in nanocomposites ranged from 4.4 to 25.7%wt (the gold content depends on the ratio of poly(VT-co-VP):Au (III)). The obtained polymer nanocomposites consist of isolated gold nanoparticles with a diameter of 1–12 nm having a predominately spherical shape, which are uniformly distributed throughout the bulk of the polymer matrix. Nanocomposites contain AuNPs of various sizes, which is determined by the ability of the polymer matrix to stabilize the different metal contents. The resulting AuNPs nanocomposites are promising materials for the design of novel hydrophilic antiseptics and antimicrobial components for medical purposes.

Full text of DOI:10.1016/j.jorganchem.2020.121352

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Water-soluble stable polymer nanocomposites with AuNPs based on the functional
poly(1-vinyl-1,2,4-triazole-co-N-vinylpyrrolidone)
A.S. Pozdnyakov, A.A. Ivanova, A.I. Emel'yanov, Yu I. Bolgova, O.M. Trofimova, G.F.
Prozorova
PII:
S0022-328X(20)30254-0
DOI:
https://doi.org/10.1016/j.jorganchem.2020.121352
JOM 121352
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 31 January 2020
Revised Date: 23 May 2020
Accepted Date: 23 May 2020
Please cite this article as: A.S. Pozdnyakov, A.A. Ivanova, A.I. Emel'yanov, Y.I. Bolgova, O.M.
Trofimova, G.F. Prozorova, Water-soluble stable polymer nanocomposites with AuNPs based on the
functional poly(1-vinyl-1,2,4-triazole-co-N-vinylpyrrolidone), Journal of Organometallic Chemistry (2020),
doi: https://doi.org/10.1016/j.jorganchem.2020.121352.
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Water-soluble stable polymer nanocomposites with AuNPs based on the
functional poly(1-vinyl-1,2,4-triazole-co-N-vinylpyrrolidone)
A.S. Pozdnyakov 1, A.A. Ivanova, A.I. Emel’yanov, Yu.I. Bolgova, O.M. Trofimova, G.F.
Prozorova.
A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, 1 Favorsky
Str., 664033 Irkutsk, Russian Federation
Abstract
New water-soluble polymer nanocomposites with gold nanoparticles (AuNPs) were
synthesized using functional copolymer of 1-vinyl-1,2,4-triazole with N-vinylpyrrolidone
(poly(VT-co-VP)) as a stabilizing matrix. The polymer AuNPs nanocomposites were studied
by transmission electron microscopy, scanning electron microscopy, ultraviolet-visible
spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, atomic absorption
and thermogravimetric analysis. The gold content in nanocomposites ranged from 4.4 to
25.7%wt (the gold content depends on the ratio of poly(VT-co-VP):Au (III)). The obtained
polymer nanocomposites consist of isolated gold nanoparticles with a diameter of 1 to 12 nm
having a predominately spherical shape, which are uniformly distributed throughout the bulk
of the polymer matrix. Nanocomposites contain AuNPs of various sizes, which is determined
by the ability of the polymer matrix to stabilize the different metal contents. The resulting
AuNPs nanocomposites are promising materials for the design of novel hydrophilic
antiseptics and antimicrobial components for medical purposes.
Keywords: 1-vinyl-1,2,4-triazole, N-vinylpyrrolidone, polymer nanocomposites, gold
nanoparticles.
1. Introduction
In the last decade, the research in new polymer composite materials, including hybrid
nanocomposites with nanoparticles of different metals are gathering momentum. For
example, gold nanoparticles are of interest due to their unique optical, electronic, catalytic
[1,2] and biological properties [3–7], applicable in various fields of science.
Since the last century, gold and its compounds have been employed in medicine for the
treatment of rheumatic and infectious diseases, including tuberculosis [8]. The development
of modern technologies has allowed to obtain gold in a nanosized state, thereby increasing its
activity in comparison with block metal. Therefore, gold was used in significantly lower
concentrations, while its properties were preserved. This enables to expand the application
scope of gold nanoparticles in the development of new biosensors and biophotonics [9–11] as
well as antibacterial [12,13] and anticancer drugs [14].
The ability of nanoparticles to penetrate into a cell strongly depends on their size and
shape [15]. The main problem is that gold nanoparticles are very unstable and prone to
aggregation [16]. Therefore, search for routes to stabilization of these particles remains a
challenge. Various high molecular compounds both natural (chitosan, cellulose,
arabinogalactan, etc.) [17,18] and synthetic (polyvinylpyrrolidone, polyacrylamide, polyvinyl
1 Corresponding author.
E-mail address: pozdnyakov@irioch.irk.ru (A.S. Pozdnyakov)
1

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alcohol, etc.) origin [19–22] are used as effective stabilizers. Application of polymers as a
stabilizing matrix not only contributes to the stabilization of nanoparticles giving them the
necessary size and shape [23,24], but also to synthesize new compounds that exhibit
synergism of the unique properties of polymers and metal nanoparticles.
Polymers of N-vinylpyrrolidone (VP) find widespread application as stabilizing
matrices of metal nanoparticles [25,26]. Also, N-vinylpyrrolidone is widely used as a
comonomer of various vinyl compounds, allowing the preparation of polymer compounds
with different functionality. 1-Vinyl-1,2,4-triazole (VT) is the most interesting comonomer,
since its polymers possess a number of valuable properties such as thermal stability and
resistance to aggressive media, ability of complex formation and quaternization,
biocompatibility and non-toxicity, etc [27–29].
Previously, we found that hydrophilic copolymers of 1-vinyl-1,2,4-triazole with N-
vinylpyrrolidone (LD50 >5000 mg/kg) are effective non-toxic platform for stabilizing silver
[30,31] and copper [32] nanoparticles. New polymer nanocomposites synthesized from
functional poly(VT-co-VP) can extend the range of nontoxic hydrophilic polymer materials
that opens up new prospects for their use in medicine.
In the present work, we report on the synthesis and characterization of new water-
soluble polymer nanocomposites based on non-toxic copolymer of 1-vinyl-1,2,4-triazole with
N-vinylpyrrolidone with different AuNPs content.
Materials and Methods
2.1. Materials
20
The initial 1-vinyl-1,2,4-triazole (VT) (bp 43 °C/3 mmHg, nD 1.5100) was
synthesized by direct vinylation of 1,2,4-triazole with acetylene in dioxane at a pressure of 14
atm.
The reaction was carried out for 4 hours at a temperature of 220 °C in the presence of a
catalyst - potassium hydroxide. The yield of VT was 78%.
20
N-Vinylpyrrolidone (99%, Sigma-Aldrich) (flash point 95 °C, nD 1.512) was used as
comonomer for the synthesis of functional copolymers. HAuCl4 (99.9%, Sigma-Aldrich) and
α,α′-azobisisobutyronitrile (AIBN) (99%, Aldrich) were used without any treatment as a
precursor of nanoparticles and radical initiator, respectively. Hydrazine hydrate (99.99%,
Sigma-Aldrich) was used as the reducing agent. Dimethylformamide (DMF), acetone and
ethanol were distilled and purified according to the known procedures.
2.2. Synthesis of 1-vinyl-1,2,4-triazole and Acrylonitrile Copolymers (poly(VT-co-VP))
Poly(VT-co-VP) was synthesized by radical copolymerization of 1-vinyl-1,2,4-triazole
and N-vinylpyrrolidone in DMF under the action of AIBN as initiator at 60 °C in argon
atmosphere. 1-Vinyl-1,2,4-triazole (1.9 g, 20.0 mmol), N-vinylpyrrolidone (2.2 g, 20.0
mmol), DMF (1 mL), and AIBN (2.0∙10–2 mol/L) were placed in ampoule. Then the mixture
2

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was stirred and kept in a thermostat at 60 °С for 1.5 h until the transparent block forms
(completion of polymerization). The reaction mixture was dissolved in DMF, precipitated
into acetone, and dried in vacuo over P2O5 at 50 °С to a constant weight. Then the product
was filtered and dissolved in water. Then the reaction mixture purified by dialyzed for 48 h
through a cellulose membrane with a pore size of 5 kDa (Cellu Sep H1, MFPI, Seguin, USA),
and freeze-dried to give copolymer as a white powder. The product yield was above than
84% and the polymer was soluble in water and dipolar organic solvents (DMF and DMSO).
Further, the obtained copolymer was used for the subsequent synthesis of the metal polymer
nanocomposites.
2.3. Synthesis of Nanocomposite based on poly(VT-co-VP) with gold nanoparticles
Poly(VT-co-VP) (1.0 g, 9.6 mmol) in water (10 mL) was added to aqueous solution (10
mL) containing HAuCl4 (0.28–11.1 g, 0.4–16.5 mmol). The reaction mixture was stirred
intensively for 30 min at room temperature. Then, aqueous solution containing N2H4 (0.05–
1.85 g, 0.2–6.0 mmol) was added dropwise over 5 min, and the mixture was stirred further
for 6 h at room temperature. The resulting solution was precipitated into ethanol. The product
was then filtered from ethanol, purified by dialysis against water through a cellulose
membrane (Cellu Sep H1, MFPI, Seguin, USA), and freeze-dried to obtain nanocomposites
as a dark-brown powder. The product yield was 79-85%. The resulting nanocomposite is
soluble in water and dipolar organic solvents (DMF, DMSO and DMAA). The gold content
in the nanocomposites was from 4.4% to 25.7%. The content of gold depends on the initial
molar ratio of stabilizing copolymer and Au(III).
2.4. Characterization
The composition and structure of the synthesized copolymers are confirmed by
elemental analysis, IR, NMR spectroscopy. Elemental analysis was performed with a Thermo
Scientific Flash 2000 CHNS-Analyzer. FTIR spectra were recorded on a Vertex 70 FT-IR in
KBr pellets. 1Н and 13С NMR spectra were recorded on a Bruker DPX-400 spectrometer (1Н,
13
400.13 MHz; С, 100.62 MHz) in DMSO-d6. The molecular weight of the copolymer was
determined by gel permeation chromatography at 50 °С using Shimadzu LC-20 Prominence
system fitted with a differential refractive index detector Shimadzu RID-20A and column
Agilent PolyPore 7.5 x 300 mm (PL1113-6500). N,N-Dimethylformamide solution was used
as the eluent at the flow rate of 1 mL/min. Dissolution of samples was performed at 50 °C for
24 h with stirring. Calibration was carried out using a series of polystyrene standards
Polystyrene High EasiVials (PL2010-0201), consisting of 12 samples with molecular weights
from 162 to 6570000 g/mol. Microphotographs were obtained on scanning electron
microscope (ТМ 3000, HITACHI). The gold content in the studied nanocomposites was
estimated by atomic absorption analysis using a Shimadzu AA-6200. X-ray diffraction
patterns (XRDs) were obtained on a powder diffractometer (D8 Advance, Bruker
Corporation, Cu radiation). Thermogravimetric analysis (TGA) and differential scanning
calorimetry (DSC) were performed using STA 449 Jupiter (Netzsch, Germany) in air
atmosphere at heating rate of 5 ºС per min, the weight of the samples was 7 mg.
Microphotographs were obtained using a transmission electron microscope (Leo 906E, Zeiss,
Germany). The water solution with 0.1 mg/mL nanocomposite concentration was used to
determine the hydrodynamic particle radius of the synthesized samples by means of the
dynamic light scattering (DLS) and electrophoretic light scattering with phase analysis
(PALS) methods, respectively, using a Zetasiser Nano-ZS photon particle analyser (Malvern
Instruments, UK). The measurements were carried out in thermostated cuvettes with
3