Sodium Tetrasulfide Research Articles

Reactive sulfur species disaggregate the SQSTM1/p62-based aggresome-like induced structures via the HSP70 induction and prevent parthanatos

Reactive sulfur species (RSS) have emerged as key regulators of protein quality control. However, the mechanisms by which RSS contribute to cellular processes are not fully understood. In this study, we identified a novel function of RSS in preventing parthanatos, a nonapoptotic form of cell death that is induced by poly (ADP-ribose) polymerase-1 and mediated by the aggresome-like induced structures (ALIS) composed of SQSTM1/p62. We found that sodium tetrasulfide (Na2S4), a donor of RSS, strongly suppressed oxidative stress-dependent ALIS formation and subsequent parthanatos. On the other hand, the inhibitors of the RSS-producing enzymes, such as 3-mercaptopyruvate sulfurtransferase and cystathionine γ-lyase, clearly enhanced ALIS formation and parthanatos. Interestingly, we found that Na2S4 activated heat shock factor 1 by promoting its dissociation from heat shock protein 90, leading to accelerated transcription of HSP70. Considering that the genetic deletion of HSP70 allowed the enhanced ALIS formation, these findings suggest that RSS prevent parthanatos by specifically suppressing ALIS formation through induction of HSP70. Taken together, our results demonstrate a novel mechanism by which RSS prevent cell death, as well as a novel physiological role of RSS in contributing to protein quality control through HSP70 induction, which may lead to better understanding of the bioactivity of RSS.

Cystine-dependent antiporters buffer against excess intracellular reactive sulfur species-induced stress

Reactive sulfur species (RSS) play a role in redox homeostasis; however, adaptive cell responses to excessive intracellular RSS are not well understood. Therefore, in this study, we generated transgenic (Tg) mice overexpressing cystathionine gamma-lyase (CSE) to produce excessive RSS. Contrary to expectations, tissue concentrations of RSS, such as cysteine persulfide (CysSSH), were comparable in both wild-type and CSE Tg mice, but the plasma concentrations of CysSSH were significantly higher in CSE Tg mice than in wild-type mice. This export of surplus intracellular RSS was also observed in primary hepatocytes of CSE Tg mice. Exposure of primary hepatocytes to the RSS generator sodium tetrasulfide (Na2S4) resulted in an initial increase in the intracellular concentration of RSS, which later returned to basal levels after export into the extracellular space. Interestingly, among all amino acids, cystine (CysSSCys) was found to be essential for CysSSH export from primary mouse hepatocytes, HepG2 cells, and HEK293 cells during Na2S4 exposure, suggesting that the cystine/glutamate transporter (SLC7A11) contributes, at least partially, to CysSSH export. We established HepG2 cell lines with knockout and overexpression of SLC7A11 and used them to confirm SLC7A11 as the predominant antiporter of CysSSCys and CysSSH. We observed that the poor efflux of excess CysSSH from the cell enhanced cellular stresses induced by Na2S4 exposure, such as polysulfidation of intracellular proteins, mitochondrial damage, and cytotoxicity. These results suggest the presence of a cellular response to excess intracellular RSS that involves the extracellular efflux of excess CysSSH by a cystine-dependent transporter to maintain intracellular redox homeostasis.

Synthesis of thiocol oligomer based on sodium tetrasulphide, epichlorhydrine and ammonium phosphate

The aim is to synthesize and study thiokol oligomer NEP-12 based on sodium tetrasulfide, epichlorohydrin and ammonium phosphate, which is intended for use as the main component of thiokol sealant. To achieve this goal, a thiokol oligomer based on sodium tetrasulfide, epichlorohydrin, and ammonium phosphate has been synthesized and investigated, and the optimal conditions for the synthesis of a thiokol oligomer have been determined. Research has been carried out on the influence of the molar ratios of the starting substances on the composition and physicochemical properties of the synthesized thiocol oligomer. 80 °C was taken as the optimum polycondensation temperature, the reaction time in this case is 1.5-2 hours, as a result, the yield of the target product reaches 94%. The thiokol oligomer with the best performance was obtained at a 1: 1: 1 molar ratio of sodium tetrasulfide, epichlorohydrin, and ammonium phosphate, respectively. Based on the results of IR spectroscopy and differential scanning calorimetry, a reaction for the formation of a thiokol oligomer is proposed.

Poly(butylene disulfide) and poly(butylene tetrasulfide): Synthesis, cure and investigation of polymerization yield and effect of sulfur content on mechanical and thermophysical properties

In this work, two polysulfide polymers were synthesized by use of 1,4-dichlorobutane and aqueous sodium disulfide or sodium tetrasulfide. The polymers were cured at 85 °C. The structural characteristics of non-cured and cured samples were identified by Raman and FT-IR spectroscopy. The morphological and the thermophysical properties of all samples were investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Also, the mechanical properties and hardness of all samples were investigated by tensile test and Shore A. Moreover, the effects of temperature and ethanol on polymerization were investigated. Aqueous monomers were characterized by UV-VIS-NIR spectroscopy. The molecular weight of the synthesized samples was determined by 1H NMR spectroscopy. The results showed that, before curing, poly(butylene tetrasulfide) (PBTS) due to amorphous structure does not have a melting peak and both polymers have a very low glass transition temperature. Without ethanol, no polymerization reaction takes place. Before curing, poly(butylene disulfide) (PBDS) is brittle and PBTS has an elastomeric behavior, but after curing PBDS also behaves as elastomer. The curing times of the two polymers are close to each other, but their mechanical properties and hardness are different.

Polysulfide-mediated sulfhydration of SIRT1 prevents diabetic nephropathy by suppressing phosphorylation and acetylation of p65 NF-κB and STAT3

Diabetic kidney disease is known as a major cause of chronic kidney disease and end stage renal disease. Polysulfides, a class of chemical agents with a chain of sulfur atoms, are found to confer renal protective effects in acute kidney injury. However, whether a polysulfide donor, sodium tetrasulfide (Na2S4), confers protective effects against diabetic nephropathy remains unclear. Our results showed that Na2S4 treatment ameliorated renal dysfunctional and histological damage in diabetic kidneys through inhibiting the overproduction of inflammation cytokine and reactive oxygen species (ROS), as well as attenuating renal fibrosis and renal cell apoptosis. Additionally, the upregulated phosphorylation and acetylation levels of p65 nuclear factor κB (p65 NF-κB) and signal transducer and activator of transcription 3 (STAT3) in diabetic nephropathy were abrogated by Na2S4 in a sirtuin-1 (SIRT1)-dependent manner. In renal tubular epithelial cells, Na2S4 directly sulfhydrated SIRT1 at two conserved CXXC domains (Cys371/374; Cys395/398), then induced dephosphorylation and deacetylation of its targeted proteins including p65 NF-κB and STAT3, thereby reducing high glucose (HG)-caused oxidative stress, cell apoptosis, inflammation response and epithelial-to-mesenchymal transition (EMT) progression. Most importantly, inactivation of SIRT1 by a specific inhibitor EX-527, small interfering RNA (siRNA), a de-sulfhydration reagent dithiothreitol (DTT), or mutation of Cys371/374 and Cys395/398 sites at SIRT1 abolished the protective effects of Na2S4 on diabetic kidney insulting. These results reveal that polysulfides may attenuate diabetic renal lesions via inactivation of p65 NF-κB and STAT3 phosphorylation/acetylation through sulfhydrating SIRT1.

Polysulfide and Hydrogen Sulfide Ameliorate Cisplatin-Induced Nephrotoxicity and Renal Inflammation through Persulfidating STAT3 and IKKβ.

Cisplatin, a widely used chemotherapy for the treatment of various tumors, is clinically limited due to its extensive nephrotoxicity. Inflammatory response in tubular cells is a driving force for cisplatin-induced nephrotoxicity. The plant-derived agents are widely used to relieve cisplatin-induced renal dysfunction in preclinical studies. Polysulfide and hydrogen sulfide (H2S) are ubiquitously expressed in garlic, and both of them are documented as potential agents for preventing and treating inflammatory disorders. This study was designed to determine whether polysulfide and H2S could attenuate cisplatin nephrotoxicity through suppression of inflammatory factors. In renal proximal tubular cells, we found that sodium tetrasulfide (Na2S4), a polysulfide donor, and sodium hydrosulfide (NaHS) and GYY4137, two H2S donors, ameliorated cisplatin-caused renal toxicity through suppression of the massive production of inflammatory cytokines, including tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and cyclooxygenase-2 (COX-2). Mechanistically, the anti-inflammatory actions of Na2S4 and H2S may be mediated by persulfidation of signal transducer and activator of transcription 3 (STAT3) and inhibitor kappa B kinase β (IKKβ), followed by decreased phosphorylation of STAT3 and IKKβ. Moreover, the nuclear translocation of nuclear transcription factor kappa B (NF-κB), and phosphorylation and degradation of nuclear factor kappa B inhibitor protein alpha (IκBα) induced by cisplatin, were also mitigated by both polysulfide and H2S. In mice, after treatment with polysulfide and H2S donors, cisplatin-associated renal dysfunction was strikingly ameliorated, as evidenced by measurement of serum blood urea nitrogen (BUN) and creatinine levels, renal morphology, and the expression of renal inflammatory factors. Our present work suggests that polysulfide and H2S could afford protection against cisplatin nephrotoxicity, possibly via persulfidating STAT3 and IKKβ and inhibiting NF-κB-mediated inflammatory cascade. Our results might shed light on the potential benefits of garlic-derived polysulfide and H2S in chemotherapy-induced renal damage.

Poly(p-xylene disulfide) and poly(p-xylene tetrasulfide): synthesis, cure and investigation of mechanical and thermophysical properties

In this work, two polysulfide polymers were synthesized using aromatic organic monomer (α,α′-dichloro-p-xylene) and sodium disulfide (Na2S2) and sodium tetrasulfide (Na2S4) aqueous monomers. Then, the curing process of the polymers was carried out at 170° C using a rheometer. The structural characteristics of synthesized and cured samples were identified by Raman and Fourier transform infrared (FT-IR) spectroscopies. Also, morphological and thermophysical properties of samples were studied by using the X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. Moreover, the molecular weight of the synthesized samples was determined by proton nuclear magnetic resonance (1H NMR). Furthermore, the mechanical properties and hardness of the samples were investigated by tensile test and Shore A. The results showed that in the noncured samples during the increase of sulfur in the polymer structure, solubility was increased whereas it decreased the hardness, melting point (Tm ) and glass transition temperature (Tg ) of polymers. But in cured samples, hardness and Tg increase by increasing sulfur and the mechanical properties also improved. This is due to the increase in crosslinks. Also, Tm and solubility are not observed due to the formation of crosslinks.

Synthesis and characterization of aliphatic polysulfides by interfacial polycondensation of sodium tetrasulfide with dichloroalkanes in the presence of quaternary onium salts

Poly(alkylenetetrasulfide) [poly(R-S4-R)] polymers with R = Me, Et, or Bu are prepared from alkylene dichloride and sodium tetrasulfide by an interfacial polycondensation technique using two quarternary ammonium salts as phase transfer catalysts. FT-IR, X-ray, and elemental analysis have characterized the synthesized polymers. Thermal properties were measured by thermogravimetric analysis and calorimetric differential scanning. Swelling procedure was used to investigate the solvent resistance of the polymers.

Repression of mercury accumulation and adverse effects of methylmercury exposure is mediated by cystathionine γ-lyase to produce reactive sulfur species in mouse brain

Reactive sulfur species (RSS), such as hydropersulfides and hydropolysulfides with high nucleophilicity, contain mobilized sulfur that readily captures xenobiotic electrophiles, leading to their sulfur adducts. We have previously reported that RSS produced by cystathionine γ-lyase (CSE) captures the electrophilic metal methylmercury (MeHg) to form inert sulfur adducts, which in turn play a critical role in the protection against MeHg-induced motor impairment in mice. However, the mechanism underlying this neuroprotective effect is not fully understood. Here, we addressed this using CSE-knockout mice. The cerebellum of CSE-knockout mice was more susceptible to MeHg than that of wild type mice. Moreover, these CSE-deficient mice exhibited a higher level of mercury accumulation in the brain. However, co-treatment with sodium tetrasulfide, an RSS able to capture MeHg, leading to the formation of its sulfur adducts, blocked the increased accumulation of mercury, motor dysfunction and mortality caused by CSE deficiency. Our findings suggest that capturing MeHg by RSS in association with its sulfur adduct formation is involved in the repression of the brain distribution and deleterious effects of MeHg.

Synthesis and characterization of methylene-xylene-based polysulfide block-copolymer/carbon nanotube nanocomposites via in situ polymerization method

ABSTRACT Good resistance to the solvent, UV radiation and excellent adhesion to surfaces are the significant features of polysulfide polymers. They are known to have extensive applications as sealants and a variety of coatings. In this work, a polysulfide copolymer was synthesized using linear and aromatic organic monomers (methylene dichloride and α,α′-dichloro-p-xylene) and sodium tetrasulfide aqueous monomer. Using carbon nanotube (CNT) modified by acid (CNTCOOH), the nanocomposites of poly(methylene-xylene tetrasulfide) (PMXTS) were synthesized via in situ polymerization. The structural characteristics of polysulfide copolymer, modified CNT and nanocomposites were identified by Fourier transform infrared (FTIR) and Raman spectroscopies. Increasingly, morphological and thermal properties of samples are studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry and thermogravimetric analysis techniques, respectively. Also, the molecular weight of the copolymer was determined by proton nuclear magnetic resonance (1H NMR). The results showed that along increasing CNTCOOHs in the nanocomposites, glass transition temperature occurs at higher temperatures, and melting temperature increased wonderfully, but did not have a significant effect on the degradation temperature. Furthermore, the copolymer is dissolved partially in dimethyl sulfoxide (DMSO) but the presence of CNTCOOHs reduces this solubility.

1,4-Naphthoquinone-mediated Activation of PTEN/Akt/CREB Signaling and Cytotoxicity are Negatively Regulated by Sodium Tetrasulfide

1,4-Naphthoquinone-mediated Activation of PTEN/Akt/CREB Signaling and Cytotoxicity are Negatively Regulated by Sodium Tetrasulfide

The Capture of Cadmium by Reactive Polysulfides Attenuates Cadmium-Induced Adaptive Responses and Hepatotoxicity.

Cadmium (Cd) is an environmental electrophile that modifies protein nucleophiles, thereby modulating cellular signaling and toxicity. While reactive persulfides/polysulfides exhibit relatively high nucleophilic properties, their roles in the altered gene expression and toxicity caused by Cd remain unclear. Exposing primary mouse hepatocytes to Cd caused heat shock protein 70 (HSP70) and metallothionein (MT)-I/II to be upregulated and cytotoxicity to occur. These effects were blocked in the presence of polysulfide sodium tetrasulfide (Na2S4). Electrospray ionization mass spectrometry analysis indicated that cadmium sulfide (CdS) and cadmium thiosulfate (CdS2O3) were produced when Cd reacted with Na2S4. Authentic CdS did not cause cellular signaling responses to be activated or hepatotoxic effects, while CdS2O3 had effects similar to those of Cd. HSP70 and MT-I/II upregulation and hepatotoxicity caused by exposure to Cd were significantly enhanced by the deletion of cystathionine γ-lyase (CSE), which catalyzes the formation of reactive persulfides/polysulfides. Deleting CSE also exacerbated Cd-mediated liver injury, whereas little hepatic damage was found when CdS or Na2S4 along with Cd was administered. Overall, the results suggest that the persulfide/polysulfide-mediated formation of sulfur adducts of Cd such as CdS rather than CdS2O3 is, at least in part, involved in decreasing the level of Cd-mediated activation of cellular signaling and toxicity.

Researches on preparation and properties of sodium polysulphide as gold leaching agent

To date, cyanide-assisted gold leaching has been considered to be the predominant method for gold extraction owing to its simple process and low cost. Increasing concerns on the toxicity of cyanide have triggered the efforts to find the non-cyanide methods to extract the gold from gold ores for the sake of environmental protection. In this work, the leaching behaviors of gold from ores by using alkaline sodium polysulphide solutions were investigated. Sodium polysulphides were prepared by hydrothermal method using sulfur and sodium sulphide nonahydrate (Na2S·9H2O) as precursor under alkaline condition. Our results show that, as-prepared polysulphide showed dual actions: as oxidant and complexant. Accordingly, alkaline sodium polysulphide system was applied to extract the trace-level gold from ores. It demonstrates that, the gold-leaching efficiency is dependent on the concentrations of sodium sulphide, the ratio of sulfur/sodium sulphide, the concentrations of sodium hydroxide, and reaction temperature. The optimized gold-extraction efficiency (85%) was achieved under following conditions: pressure of 1atm; ratio of liquid to solid at 5:1; the concentration of sodium sulphide and sodium hydroxide at 90g/L and 0.8M, respectively; the sulfur/sodium sulphide ratio at 3; reaction temperature at 80°C; reaction time for 1h. To reveal how the composition of sodium polysulphide affects the gold leaching, the phases of polysulphide were characterized by combing X-Ray Powder Diffraction, Laser-Raman Spectrum, and Electrochemical methods. The results indicated that, as-prepared sodium polysulphide mainly comprises of the sulfur, sodium trisulfide, sodium tetrasulfide and sodium pentasulfide, wherein the tetrasulfide and pentasulfide are the main activate reagents for gold leaching. The finding in this work indicates that, the sodium polysulphide could have a good capability for Au extraction from Au-bearing antimony ore.

Synthesis and characterization of ethylene-xylene-based polysulfide block-copolymers using the interfacial polymerization method

ABSTRACTCopolymers of linear and aromatic polysulfide blocks are synthesized using interfacial polymerization of dichloro-xylene-based aromatic and ethylene-dichloride-based non-aromatic organic monomers. Synthesized copolymers consist of poly(ethylene sulfide) as well as ploy (xylene sulfide) blocks. Fascinating properties of linear and aromatic polysulfide species are gathered in the structure of synthesized polysulfide copolymers. Ethylene dichloride and α,α′-dichloro-p-xylene are used as the non-aromatic and aromatic organic monomers, respectively. To investigate the influences of sulfur contents in the backbone of the polymer on the thermal stability of synthesized copolymers, poly(ethylene-xylene disulfide) (PEXDS), poly(ethylene-xylene trisulfide) (PEXTRS) and poly(ethylene-xylene tetrasulfide) (PEXTS) copolymers are synthesized using, respectively, sodium disulfide, sodium trisulfide and sodium tetrasulfide, as aqueous monomers. Compared to both linear and nonlinear homopolymers, synthesized copolymers exhibit improved thermal stability. Moreover, the thermal degradation temperatures of synthesized copolymers improve by decreasing the number of sulfur atoms in the backbone of copolymers. These results reveal that thermal degradation of polysulfide copolymers can be tailored by controlling the polysulfide chain’s sulfur contents. Structural characteristics of synthesized polysulfide copolymers are also investigated using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and X-ray diffraction analysis.

Synthesis and characterization of poly(ethylene tetrasulfide)/graphene oxide nanocomposites by in situ polymerization method

ABSTRACTPoly(ethylene tetrasulfide) (PSP) is synthesized via interfacial polycondensation of 1,2 dichloroethane and sodium tetrasulfide, in the presence of graphene oxide (GO). This process resulted in homogeneously dispersed PSP/GO nanocomposites. Nanocomposites of 0.3 and 0.5 wt% of GO are synthesized and their morphology, chemical characteristics behavior are studied employing field emission scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques. Thermal characterization of composites is performed by differential scanning calorimetry and thermogravimetry analysis. Results indicate that the addition of only small amounts (0.5 wt%) of well-dispersed GO can increase the melting point more than 16°C resulting in better thermal properties for the composite. The solubility of nanocomposite is also studied and results show that the solubility depends on solvent concentration in addition to reinforcement (GO) deals.

Encapsulation of red sulfur chromophores in a zeolitic imidazolate framework (ZIF-8) via solvent assisted linker exchange

Red color sulfur chromophores were entrapped inside the cages of zeolitic imidazolate framework ZIF-8 in order to prepare a ZIF analog of ultramarine red. ZIF-8 is made from Zn2+ and 2-methylimidazole linker and has sodalite topology. SIM-1, a ZIF isostructural to ZIF-8 that is made from Zn2+ and an imidazole linker containing a carboxaldehyde group was used as the starting material for the red pigment preparation. SIM-1 was converted to ZIF-8 via solvent assisted linker exchange (SALE) in DMF in the presence of sodium tetrasulfide as the sulfur source. The polysulfide was oxidized into the red sulfur chromophore S4 due to the presence of the carboxaldehyde group of the SIM-1 linker under the reaction conditions. During the transformation, the red sulfur species were successfully trapped inside the ZIF-8 cages generating a stable red solid pigment. To the best of our knowledge, this is the first example of low temperature ultramarine pigment preparation process. The red pigments were characterized by using PXRD, FTIR, UV–Vis, XPS and SEM.

Conformational analysis and chemical reactivity of the multidomain sulfurtransferase, Staphylococcus aureus CstA.

The cst operon of the major human pathogen Staphylococcus aureus (S. aureus) is under the transcriptional control of CsoR-like sulfurtransferase repressor (CstR). Expression of this operon is induced by hydrogen sulfide, and two components of the cst operon, cstA and cstB, protect S. aureus from sulfide toxicity. CstA is a three-domain protein, and each domain harbors a single cysteine that is proposed to function in vectorial persulfide shuttling. We show here that single cysteine substitution mutants of CstA fail to protect S. aureus against sulfide toxicity in vivo. The N-terminal domain of CstA exhibits thiosulfate sulfurtransferase (TST; rhodanese) activity, and a Cys66 (34)S-persulfide is formed as a catalytic intermediate in both the presence and absence of the adjacent TusA-like domain using (34)S-SO3(2-) as a substrate. Cysteine persulfides can be trapped on both C66 in CstA(Rhod) and on C66 and C128 in CstA(Rhod-TusA) when incubated with thiosulfate, sodium tetrasulfide (Na2S4), and in situ persulfurated SufS. C66A substitution in CstA(Rhod-TusA) abolishes C128 S-sulfhydration, consistent with directional persulfide shuttling in CstA. Fully reduced CstA(Rhod-TusA) is predominately monomeric, and high resolution tandem mass spectrometry reveals that Cys66 and Cys128 can form a C66-C128 disulfide bond using a number of oxidants, which leads to a significant change in conformation. A competing intermolecular C128-C128' disulfide bond is also formed. Small-angle X-ray scattering measurements and gel filtration chromatography of reduced CstA(Rhod-TusA) reveal an elongated molecule (Rg ≈ 30 Å, 21.6 kDa) where the two domains pack "side-by-side" that likely places Cys66 and Cys128 far apart. These studies are consistent with the low yield of C66-C128 cross-link as a mimic of a persulfide transfer intermediate in CstA, and small, but measurable persulfide transfer from Cys66 to Cys128 within the CstA(Rhod-TusA) with inorganic sulfur donors.

Use of Carbon Nanotube to Enhance Thermal Resistance of Poly(ethylenetetrasulfide) via in situ Polymerization Method

Poly(ethylenetetrasulfide)/multi-walled carbon nanotubes (PETS/MWCNTs) nanocomposite was synthesized from ethylene dichloride and sodium tetrasulfide monomers via in situ polymerization method. The samples were characterized by different techniques including Raman and Fourier transform infrared spectroscopy, scanning electron and atomic force microscopy and X-ray diffraction. XRD results prove that the presence of MWCNTs increases the crystalline content of nanocomposites compared to pure PETS. Thermal behavior of nanocomposites is also studied by differential scanning calorimetry and thermogravimetric analysis methods. The results show better thermal stability, higher glass transition and melting point temperature in comparison with pure polysulfide polymer, which is of considerable interest for this polymer. The degradation kinetics for nanocomposites was also analyzed employing Friedman method.

Preparation of synthesized sulfide polymer through phase-transfer catalyzed polycondensation of ethylene dibromide and sodium tetrasulfide: characterization, thermal and rheological properties

Sulfide polymers were obtained through the interfacial polymerization of sodium tetrasulfide and ethylene dibromide. The polymerization process was carried out under interfacial condition using two phase-transfer catalysts: methyl-tributyl ammonium bromide and methyl-tributyl ammonium chloride. The polymer characteristics were examined by attenuated total reflectance- fourier transform infrared spectroscopy, elemental analysis (CHNS/O) and X-ray diffraction methods. Thermal characteristics were investigated by differential scanning calorimetry and thermogravimetric analysis methods. The rheological behavior of the synthesized sulfide polymer during curing reaction, and isothermal time dependency of elastic storage modulus, G′, at different temperatures and constant shear frequency was studied using a stress-controlled rheometer. Moreover, the solvent resistance of synthesized polymer was investigated through the swelling method.

New Role of Layered Silicates as Phase Transfer Catalyst for In Situ Polymerization of Poly(ethylenetetrasulfide) Nanocomposite

In this study, polyethylenetetrasulfide/montmorillonite nanocomposite (PETS/nanoclay) is synthesized from ethylene dichloride and sodium tetrasulfide monomers by in situ polymerization method. The effect of phase-transfer catalyst (PTC) on polymerization kinetics in addition to the structure of resulting PETS containing nanoclay is investigated. The results show that surface-modified montmorillonites by methyl tallow bis-2-hydroxyethyl quaternary ammonium chloride could properly act as PTC. Therefore, it is demonstrated that the addition of nanoclay as PTC reduces the reaction time and increases the polymerization rate during the production of final nanocomposite. The samples were characterized using Fourier transform infrared and Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), nuclear magnetic resonance spectroscopy besides energy-dispersive X-ray spectroscopy (EDS) combined with SEM (SEM–EDX). In addition, thermal behavior of nanocomposite was perused by differential scanning calorimetry and thermogravimetric analysis. XRD and AFM results show proper dispersion of clay in PETS matrix and SEM–EDX results demonstrate suitable distribution of clay in polymer matrix. PETS/nanoclay nanocomposite show a better thermal stability, and also higher glass transition and melt temperature compared to pure polysulfide polymer. The solubility of nanocomposite is also studied and results show that the solubility depends on solvent concentration in addition to reinforcement (nanoclay) deals.